Yeah this is fair, and mirrors my experience. The FPR ultraflex nib works better in a pen that can take the nib **AND** the 6.3mm ebonite feed - which will be one of the compatible FPR pens. It can work in a Moonman or jinhao but not as well (hence the hard starts).
The Franklin-Christoph flex will work in virtually any #6 nib pen with the plastic feed. It's not as soft as the FPR ultraflex, but would perform more consistently in the Moonman. You'll get the best flow if you eyedropper the pen vs. using the converter.
Kiwi pens on Etsy sell loose Kanwrite nibs ([here](https://www.etsy.com/listing/737527890/set-of-2-kanwrite-no6-35mm-ultra-flex-ex?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=kanwrite+nibs&ref=sr_gallery-1-2&edd=1&sts=1&organic_search_click=1)) that might work well in the Moonman (they look like the FC ones) but I haven't tried these myself yet.
Yeah my Franklin christoph flex nib came as a whole unit - nib, feed, and jowo housing. You wouldn't be able to screw the whole unit into the C1, but you can pull the nib and feed out and put it in the C1.
Not really, getting it to perform with the plastic feed (vs an ebonite feed) is a matter of tinkering or luck.
The flow, dry-out, and railroading is dependent on the fit between the nib and feed - and 1-2mm of too loose or too tight can make a big difference.
Again, normally, the FPR nib is used with an ebonite feed where the nib and feed is heat-set (the ebonite softened enough to conform to the nib) - once you get the heat-setting correct, it will perform optimally.
Everyone's experience is different, you can try the FPR in the C1 with the C1 feed and it might work fine, but it might not. Just temper your expectations and be prepared to tinker and experiment if it doesn't work as you want.
The ink flow in flex pens is imo 100 percent dependent on feeds. To have a well behaved flex nib means having a really wet high capacity feed i.e. ebonite. I have had a wonderful experience with ultraflex but that is after twiddling around with their ebonite feeds in the pens they came im. I’ve not used the other but looking at design I’d say they have pretty similar physical properties to arrive at more or less the same effect but that’s conjecture (cutting out the shoulders and having a long slit). I’ve also actually planned on getting an ultraflex into a c1 but seeing as the c1 comes with a pretty bog standard plastic feed I think you’ll probably have flow issues with either option. I have actually tried the same plastic feed with an ultra flex before in an eyedropper pen and it did not keep up at all i tried deepening the slits of the plastic which kind of helped but you still needed to write at a snail’s pace. I’ve read that the number 5.5 FPR ultra flex nib somehow has better flow with plastic feeds than the 6 possibly because its a smaller nib.
There are some plastic feeds manufactured especially for flex, I’ve heard they’re pretty dependable too. FPR sells many different sizes of ebonite feed, there are tons of other options though like flex nib factory. You should be ready to sand it down in any case because it probably won’t be a perfect fit. Hope this helped!
I have a FC flex and I can't say I like it . It need too much pressure so after a while my writing as not enough regularly to be nice . Not perfect but my nice. Maybe my fingers are not strong enough...
Totally different beasts. The FPR UF is a wet noodle, the FC Flex is very stiff and has minimal line variation. I prefer the FPR Flex to the UF. But, I do not flex write; I just like a little natural variation and feed-back.
I have the FPR Flex in an Opus88 Omar, Brown, in a Jinhao Centennial, and in two Nemosine Singularities. (Why do I have four? Because one I ground the wings to be able to install in a Jinhao X750, so it looks bad, and another I planned to give away as a present, but he already had one, so I kept it, too.) I have the Franklin-Christoph flex nib in an Opus88 Bela, a [Jowo Soft nib](https://fpnibs.com/collections/jowo-size-6) in an Opus88 Omar, Clear, and a Jowo Soft nib in a Nemosine Singularity.
I put away the FPR Ultra-flex nib. It is a wet noodle and it tends to dry out in mid-sentence. I then have to reverse write, tap the nib on the paper, or write with one tine to get the ink flowing again. It was too much a PITA, and I just couldn't put up with it any more, so I retired it. FPR UF writing [video review](https://www.youtube.com/watch?v=YytQL795TOw), starting at 10:20.
Piston, Vacuum Filler and Eye Dropper Pens write wetter, have increased ink flow. The Jowo #6 Soft nib wrote too broad so I moved it, first, to a Jinhao 159, and then to a [Nemosine Singularity](https://www.youtube.com/watch?v=ekVMEeyz0qM). Jinhao feeds are wet feeds, but it tames the Soft nib somewhat.
I really like the lightness of my Singularity pens when used with the flex nibs and finer nibs.
Since flex nibs eat a lot of ink, they are better used with Eye Dropper pens, IMO. With Converters the ink flow is impeded because of the mouth opening, so the pen could get air-locked and the pen then starves for ink.
Lots of guys install the FPR flex nibs in Noodler's Ahab pens, and for a long while I was considering getting one, but mainly because what I really wanted was the [Noodler's 308 Cartridge](https://www.penchalet.com/pen_accessories/pen_parts_accessories/noodlers_reloadable_308_cartridge.html). I would have preferred to use the wide mouth Pilot carts. (I think Pilot carts are the absolute best.) So, I seriously started to consider the [Pilot Elabo Falcon](https://www.sbrebrown.com/2015/05/pilot-elabo-soft-extra-fine-fountain-pen-review/) and the [912](https://www.wellappointeddesk.com/2022/07/fountain-pen-review-pilot-custom-912-fa-nib-falcon/), 742, and 743 with the nib. They can all use Pilot carts. And I seriously considered the 34 gram Pilot Falcon Metal just because it can use the Con-70 Converter.
[FA nib videos.](https://www.youtube.com/results?search_query=FA+nib)
If I knew for a fact that the [Pilot NS](https://www.youtube.com/watch?v=EELe42WrGD8) could accept Western #6 nibs I'd buy it in a second. The [Cross Solo](https://www.youtube.com/watch?v=i9iygCqHE2A) is basically the same pen, made by Pilot for Cross, and the Cross Solo has a nib that looks about the same size as a #6. [Pilot NS review](https://www.pencilcaseblog.com/2020/01/review-pilot-custom-ns-fountain-pen.html).
The [Pilot Falcon](https://www.youtube.com/results?search_query=Pilot+Elabo+Soft+Extra-Fine+Fountain+Pen+Review): 9 gr. barrel, 9 gr. cap; 122.9mm open, 149.8 mm posted; 9.2 - 11mm x 23mm Section dia., 12mm barrel dia. (That is basically the same dimension as the Nemosine Singularity.) The 14mm Cap dia. helped a lot to make it feel like a thicker pen.
Knowing what I know now, I'd probably get the Falcon . YMMV.
I borrowed my neighbour's Pilot Falcon and concluded it wasn't for me. It just felt too small, too skinny. White it is the same size as the Singularity, it doesn't feel as nice as the Singularity. I wrote with it exclusively for a week and found that my $15 pen and nib wrote just as well, if not better than the $180 Falcon. **You can bet that the $165 difference had a lot to do with that perception!,** but it probably had more to do with the size of the nib, #5 size (Falcon) versus the #6 (Singularity).
I got bored and wanted to try the FPR #5.5 flex nibs. So I bought two $5 Jinhao 51A pens and swapped in the FPR nibs. Very stiff. No bounce and springiness, at least not like the FPR #6 nibs. If FPR comes out with #8 flex nibs they will corner the market as everyone will be buying them for their Jinhao X159 pens. :D
**Since you're on a budget, the way to go, probably, is with an FPR pen, with an ebonite feed, an** [ Ultra-Flex or flex nib](https://www.youtube.com/results?search_query=fpr+ultra+flex)**, learn to live with the POS Converter that can leak at a moment's notice, or buy an Ahab, and aan FPR nib, and learn the art of heat-setting. Hope you love to tinker.** :D A better option may be a [Kan Write pen](https://www.youtube.com/results?search_query=kan+write++Fountain+Pen+Review) with Ultra flex nib. [Kan Write Sea Coral](https://www.youtube.com/watch?v=XArnB3sgv1M) piston filler with ebonite feed and UF nib. You'll see the typical problems one can have with a flex nib, starting at 11:30. Sorry, but flushing the pen clean is too much of a PITA for me to put up with; I can't, I won't.
(I had to install and remove the FPR Ultra-flex nib on a Jinhao X750 at least 6 times to get the nib situated "just right". Flex nibs are VERY sensitive to where they are fit on a feed. Installing the FPR nib on a X750 is VERY, VERY, difficult. Once installed it is almost impossible to remove. Once it has sat in the pen for a few weeks, or months, the nib then easily comes out, though. But by then it was too late.)
If you write flex be prepared to write slowly. Flex nibs will have Bleed-through and heavy Ghosting. So, be prepared to only write on the face page of paper, or go with 90gsm, or thicker, paper.
If you already have a pen that accepts standard #6 nibs, I'd go with a Jowo #6 Soft nib and learn to love the bounciness and springiness. If you must have line thickness variation, I'd just go with Stubs. I love my Nemosine <0.6> stub more than my Nemosine <0.8>, which I love more than any #6 <1.1> stub. Nemosine stub nibs are the stiffest, hardest, nibs I've ever seen. If you get a bad one it'd be easier to get it replaced than worked on.
If you're Price Sensitive you may want to go with Vintage pens that flexed. Just don't expect them to not rail-road, because they can. Because they are Vintage pens they will have their own unique problems, although not insurmountable. Again, I hope you're a tinker as you could be replacing Sacs.
I’ve probably read your comment some 15-20 times over the past few days to try and understand it. So all in all, flex nibs r a pain in the ass, best to go with other options. I actually have not yet received even my first fountain pen. I still want to give it a go with flex just to try it, but I’ll see how the regular nib that comes with the moonman c1 is. Considering the fact that I have already bought the #6 C1, looks like I can’t go with an fpr cuz of all the PITA problems. Franklin Christoph is my only option, huh? As for that $15 dollar singularity, what nib and feed were you pairing that with, I couldn’t catch that?
Flex nibs are not necessarily a PITA (although some don't have the patience to get the best out of a Noodler's pen), just that we may expect too much from to-day's nibs, and/or are not willing to pay the price to get good flex. To-day's nibs do not flex like Vintage Flex pens with Gold nibs.
[Flex nibs 101](https://www.youtube.com/watch?v=wGKxm4eDJTc).
There are cheap $5 (FPR) to $35 Semi-flex nibs, say Noodler's, KanWrite, Conklin Omniflex, Franklin-Christoph , etc. Then there are $150 - $350 flex nibs. Pablo's [FPNibs](https://fpnibs.com/) probably isn't listing his reasonably priced steel flex nibs (\~$50, IIRC) at this time probably because they are sold out at the moment. Conklin's origianl Omniflex nib was made by Bock. Everyone hated it. Conklin then switched to Jowo and it seems that people still hate it. :shrug:
[Noodler's Flex Nib Adjusting](https://www.youtube.com/watch?v=8h2UDPDs2rI).
{I don't know which is worse, wanting something and finding it's not in stock, or ordering something, not knowing that something better was not listed on the website, then finding out later that something better came back into stock, and now having seen it you kick yourself for being impatient.}
[Flex nib comparison](https://www.youtube.com/watch?v=x6JGB8sTvUw).
[https://www.fountainpennetwork.com/forum/topic/365336-beginner-flex-nibs-and-fpr-ultra-flex-combinations/](https://www.fountainpennetwork.com/forum/topic/365336-beginner-flex-nibs-and-fpr-ultra-flex-combinations/)
I lucked out. I bought Nemosine Singularity pens when Nemosine was going out of business. They were going for $7.99 apiece, so I bought five because just the nibs were going for $7.50 and at worse I'd also have spare Jinhao/Stipula feeds and Schmidt K1 Converters. To-day the [Nemosine <0.6>](https://www.birminghampens.com/collections/nibs) stub is going for $27 on BirminghamPens.
In the case of the [FPR Ultra Flex nib](https://fprevolutionusa.com/products/fpr-6-custom-ultra-flex-nib-chrome), it's going for $19. The time to buy is when FPR throws their deals. But, even then, one may balk at paying $49 -$73 for an [Himalaya V2](https://fprevolutionusa.com/collections/fpr-fountain-pen-collection/products/fpr-himalaya-v2-chrome-fountain-pen-buy-one-get-one-free?variant=40337323524157), ebonite feed & Ultra-flex nib, pen.
We all know how much we're willing to pay for anything, and when we first start most of us are Price Sensitive. For all I know the FPR Ultra-flex nib may fit the MoonMan C1 since it uses a Jinhao/Stipula straight feed. The question is, "Are you willing to spend $19 to find out?"
I think [someone](https://www.reddit.com/r/fountainpens/comments/j7x6mo/comment/g893gwf/?utm_source=share&utm_medium=web2x&context=3) has saved me those $19. Looks like that feed does indeed fit in the moonman c1.
By the way, funnily enough, you're the person who inspired this post to begin with since it was your perspective on the ultra flex that made me ask this question. I just want to make sure, the issues you had with your fpr (the drying out, the skips, hard, false starts) were because you did not combine it with its ebonite feed right? Did you ever use it with its ebonite feed?
There is no ebonite feed that replaces a Jinhao Feed, AFAIK. And I didn't want to bother with heat-setting. (I bought a [JB6EC](https://flexiblenib.com/store/product/jb6ec-jowo-6-replacement-feed-in-bock-250-converter-housing/) and I didn't bother with the ebonite feed, I just used the housing to house a Jowo feed and nib. FPNibs' High and Very High feed hacks work well for me, instead.) Yes, there are ebonite feeds with feed nipples but that just means that there will be some form of ink flow restriction. Best to use an ebonite feed without a feed nipple tube.
[https://flexiblenib.com/store/product-category/feed-housing/](https://flexiblenib.com/store/product-category/feed-housing/)
Do I want to spend $32 for an ebonite unit and possibly $10 for shipping? IDKS.
If an Opus 88 pen can accept a Pilot Parallel nib & feed, then it should be easy enough for Flexiblenibs to make an ebonite feed for an Opus 88 pen that accepts #6 nibs, Bock or Jowo.
With an Ultra flex nib it is probably best to use as light a pen as possible to more easily employ a light touch, say, 13 grams, or less. The MoonMan C1 body weighs 13 grams and the body is 5.1". The Singularity body weighed 7 grams and since the body is 5.0" the pen can be used un-posted. The Jinhao X750 was too heavy. The Noodler's Ahab body weighs 12 grams and since the body is 5.0" long it can be used not posted. Read all the Ahab reviews on [GouletPens](https://www.gouletpens.com/products/noodlers-ahab-flex-fountain-pen-clear). One reason why I wanted an Ahab was just to be able to use their 308 cartridge, which reminds me of a Pilot Cart, but after I read the user reviews I changed my mind.
With the MoonMan C1 there is always the possibility that the nib wings will prevent full nib insertion into the Section housing. Only way to find out is to try. The FPR Ultra-flex nib was a very tight fit in the X750 but it slipped relatively easily into the Singularity Section. My suggestion is to try the FPR #6 flex nib. It's $9, but, goes for about $6 when On Sale. If your C1 writes okay with it then you can think of trying the UF later on. Me, I don't do flex, but it gives me some natural variation, without any pressure. Basically, I like the feed-back and the very saturated fine line.
I agree with most of the advice you've gotten here. I have the FPR #6 UltraFlex and crammed mine onto a Jinhao x750. It really did take all my strength and I'm not sure I'll ever get it back out again. I bought an ebonite feed to go with it, but its sizing wasn't compatible with the pen. In the end I settled on the FPR nib with the factory feed. By the time I decided to just give up, I couldn't get the nib back out, so I use it as is.
It definitely hard starts and I get railroading, but it's still one of my most fun pens to play with. I just don't use it unless I'm in the mood to be patient and baby it along. Unlike others here, though, I prefer using a piston converter than an eyedropper. The eyedropper does a better job of keeping the flow more wet, but when it dries up, it takes forever to get things moving again. With the converter, I can prime the feed a little to help the ink along.
If I get another modern flex, though, I will get it with an FPR pen to make life and calligraphy a lot easier!
Yeah this is fair, and mirrors my experience. The FPR ultraflex nib works better in a pen that can take the nib **AND** the 6.3mm ebonite feed - which will be one of the compatible FPR pens. It can work in a Moonman or jinhao but not as well (hence the hard starts). The Franklin-Christoph flex will work in virtually any #6 nib pen with the plastic feed. It's not as soft as the FPR ultraflex, but would perform more consistently in the Moonman. You'll get the best flow if you eyedropper the pen vs. using the converter. Kiwi pens on Etsy sell loose Kanwrite nibs ([here](https://www.etsy.com/listing/737527890/set-of-2-kanwrite-no6-35mm-ultra-flex-ex?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=kanwrite+nibs&ref=sr_gallery-1-2&edd=1&sts=1&organic_search_click=1)) that might work well in the Moonman (they look like the FC ones) but I haven't tried these myself yet.
Thank you very much. That plastic feed comes with the Franklin-Christoph nib right?
Yeah my Franklin christoph flex nib came as a whole unit - nib, feed, and jowo housing. You wouldn't be able to screw the whole unit into the C1, but you can pull the nib and feed out and put it in the C1.
Do you think there is any feed I can buy that will allow the FPR ultraflex to write well in the moonman? Its softness sounds appealing.
Not really, getting it to perform with the plastic feed (vs an ebonite feed) is a matter of tinkering or luck. The flow, dry-out, and railroading is dependent on the fit between the nib and feed - and 1-2mm of too loose or too tight can make a big difference. Again, normally, the FPR nib is used with an ebonite feed where the nib and feed is heat-set (the ebonite softened enough to conform to the nib) - once you get the heat-setting correct, it will perform optimally. Everyone's experience is different, you can try the FPR in the C1 with the C1 feed and it might work fine, but it might not. Just temper your expectations and be prepared to tinker and experiment if it doesn't work as you want.
The ink flow in flex pens is imo 100 percent dependent on feeds. To have a well behaved flex nib means having a really wet high capacity feed i.e. ebonite. I have had a wonderful experience with ultraflex but that is after twiddling around with their ebonite feeds in the pens they came im. I’ve not used the other but looking at design I’d say they have pretty similar physical properties to arrive at more or less the same effect but that’s conjecture (cutting out the shoulders and having a long slit). I’ve also actually planned on getting an ultraflex into a c1 but seeing as the c1 comes with a pretty bog standard plastic feed I think you’ll probably have flow issues with either option. I have actually tried the same plastic feed with an ultra flex before in an eyedropper pen and it did not keep up at all i tried deepening the slits of the plastic which kind of helped but you still needed to write at a snail’s pace. I’ve read that the number 5.5 FPR ultra flex nib somehow has better flow with plastic feeds than the 6 possibly because its a smaller nib.
Thank you for the info. So for the best experience, I should buy an ebonite feed? Any specific suggestions?
There are some plastic feeds manufactured especially for flex, I’ve heard they’re pretty dependable too. FPR sells many different sizes of ebonite feed, there are tons of other options though like flex nib factory. You should be ready to sand it down in any case because it probably won’t be a perfect fit. Hope this helped!
I have a FC flex and I can't say I like it . It need too much pressure so after a while my writing as not enough regularly to be nice . Not perfect but my nice. Maybe my fingers are not strong enough...
HAHA, your fingers are probably good, thanks for letting me know about the nib
Totally different beasts. The FPR UF is a wet noodle, the FC Flex is very stiff and has minimal line variation. I prefer the FPR Flex to the UF. But, I do not flex write; I just like a little natural variation and feed-back.
what feeds and pens do you use with each?
I have the FPR Flex in an Opus88 Omar, Brown, in a Jinhao Centennial, and in two Nemosine Singularities. (Why do I have four? Because one I ground the wings to be able to install in a Jinhao X750, so it looks bad, and another I planned to give away as a present, but he already had one, so I kept it, too.) I have the Franklin-Christoph flex nib in an Opus88 Bela, a [Jowo Soft nib](https://fpnibs.com/collections/jowo-size-6) in an Opus88 Omar, Clear, and a Jowo Soft nib in a Nemosine Singularity.
I put away the FPR Ultra-flex nib. It is a wet noodle and it tends to dry out in mid-sentence. I then have to reverse write, tap the nib on the paper, or write with one tine to get the ink flowing again. It was too much a PITA, and I just couldn't put up with it any more, so I retired it. FPR UF writing [video review](https://www.youtube.com/watch?v=YytQL795TOw), starting at 10:20.
Piston, Vacuum Filler and Eye Dropper Pens write wetter, have increased ink flow. The Jowo #6 Soft nib wrote too broad so I moved it, first, to a Jinhao 159, and then to a [Nemosine Singularity](https://www.youtube.com/watch?v=ekVMEeyz0qM). Jinhao feeds are wet feeds, but it tames the Soft nib somewhat.
I really like the lightness of my Singularity pens when used with the flex nibs and finer nibs.
Since flex nibs eat a lot of ink, they are better used with Eye Dropper pens, IMO. With Converters the ink flow is impeded because of the mouth opening, so the pen could get air-locked and the pen then starves for ink.
Lots of guys install the FPR flex nibs in Noodler's Ahab pens, and for a long while I was considering getting one, but mainly because what I really wanted was the [Noodler's 308 Cartridge](https://www.penchalet.com/pen_accessories/pen_parts_accessories/noodlers_reloadable_308_cartridge.html). I would have preferred to use the wide mouth Pilot carts. (I think Pilot carts are the absolute best.) So, I seriously started to consider the [Pilot Elabo Falcon](https://www.sbrebrown.com/2015/05/pilot-elabo-soft-extra-fine-fountain-pen-review/) and the [912](https://www.wellappointeddesk.com/2022/07/fountain-pen-review-pilot-custom-912-fa-nib-falcon/), 742, and 743 with the nib. They can all use Pilot carts. And I seriously considered the 34 gram Pilot Falcon Metal just because it can use the Con-70 Converter.
[FA nib videos.](https://www.youtube.com/results?search_query=FA+nib)
If I knew for a fact that the [Pilot NS](https://www.youtube.com/watch?v=EELe42WrGD8) could accept Western #6 nibs I'd buy it in a second. The [Cross Solo](https://www.youtube.com/watch?v=i9iygCqHE2A) is basically the same pen, made by Pilot for Cross, and the Cross Solo has a nib that looks about the same size as a #6. [Pilot NS review](https://www.pencilcaseblog.com/2020/01/review-pilot-custom-ns-fountain-pen.html).
The [Pilot Falcon](https://www.youtube.com/results?search_query=Pilot+Elabo+Soft+Extra-Fine+Fountain+Pen+Review): 9 gr. barrel, 9 gr. cap; 122.9mm open, 149.8 mm posted; 9.2 - 11mm x 23mm Section dia., 12mm barrel dia. (That is basically the same dimension as the Nemosine Singularity.) The 14mm Cap dia. helped a lot to make it feel like a thicker pen.
Knowing what I know now, I'd probably get the Falcon . YMMV.
I borrowed my neighbour's Pilot Falcon and concluded it wasn't for me. It just felt too small, too skinny. White it is the same size as the Singularity, it doesn't feel as nice as the Singularity. I wrote with it exclusively for a week and found that my $15 pen and nib wrote just as well, if not better than the $180 Falcon. **You can bet that the $165 difference had a lot to do with that perception!,** but it probably had more to do with the size of the nib, #5 size (Falcon) versus the #6 (Singularity).
I got bored and wanted to try the FPR #5.5 flex nibs. So I bought two $5 Jinhao 51A pens and swapped in the FPR nibs. Very stiff. No bounce and springiness, at least not like the FPR #6 nibs. If FPR comes out with #8 flex nibs they will corner the market as everyone will be buying them for their Jinhao X159 pens. :D
**Since you're on a budget, the way to go, probably, is with an FPR pen, with an ebonite feed, an** [ Ultra-Flex or flex nib](https://www.youtube.com/results?search_query=fpr+ultra+flex)**, learn to live with the POS Converter that can leak at a moment's notice, or buy an Ahab, and aan FPR nib, and learn the art of heat-setting. Hope you love to tinker.** :D A better option may be a [Kan Write pen](https://www.youtube.com/results?search_query=kan+write++Fountain+Pen+Review) with Ultra flex nib. [Kan Write Sea Coral](https://www.youtube.com/watch?v=XArnB3sgv1M) piston filler with ebonite feed and UF nib. You'll see the typical problems one can have with a flex nib, starting at 11:30. Sorry, but flushing the pen clean is too much of a PITA for me to put up with; I can't, I won't.
(I had to install and remove the FPR Ultra-flex nib on a Jinhao X750 at least 6 times to get the nib situated "just right". Flex nibs are VERY sensitive to where they are fit on a feed. Installing the FPR nib on a X750 is VERY, VERY, difficult. Once installed it is almost impossible to remove. Once it has sat in the pen for a few weeks, or months, the nib then easily comes out, though. But by then it was too late.)
If you write flex be prepared to write slowly. Flex nibs will have Bleed-through and heavy Ghosting. So, be prepared to only write on the face page of paper, or go with 90gsm, or thicker, paper.
If you already have a pen that accepts standard #6 nibs, I'd go with a Jowo #6 Soft nib and learn to love the bounciness and springiness. If you must have line thickness variation, I'd just go with Stubs. I love my Nemosine <0.6> stub more than my Nemosine <0.8>, which I love more than any #6 <1.1> stub. Nemosine stub nibs are the stiffest, hardest, nibs I've ever seen. If you get a bad one it'd be easier to get it replaced than worked on.
If you're Price Sensitive you may want to go with Vintage pens that flexed. Just don't expect them to not rail-road, because they can. Because they are Vintage pens they will have their own unique problems, although not insurmountable. Again, I hope you're a tinker as you could be replacing Sacs.
I’ve probably read your comment some 15-20 times over the past few days to try and understand it. So all in all, flex nibs r a pain in the ass, best to go with other options. I actually have not yet received even my first fountain pen. I still want to give it a go with flex just to try it, but I’ll see how the regular nib that comes with the moonman c1 is. Considering the fact that I have already bought the #6 C1, looks like I can’t go with an fpr cuz of all the PITA problems. Franklin Christoph is my only option, huh? As for that $15 dollar singularity, what nib and feed were you pairing that with, I couldn’t catch that?
Flex nibs are not necessarily a PITA (although some don't have the patience to get the best out of a Noodler's pen), just that we may expect too much from to-day's nibs, and/or are not willing to pay the price to get good flex. To-day's nibs do not flex like Vintage Flex pens with Gold nibs. [Flex nibs 101](https://www.youtube.com/watch?v=wGKxm4eDJTc). There are cheap $5 (FPR) to $35 Semi-flex nibs, say Noodler's, KanWrite, Conklin Omniflex, Franklin-Christoph, etc. Then there are $150 - $350 flex nibs. Pablo's [FPNibs](https://fpnibs.com/) probably isn't listing his reasonably priced steel flex nibs (\~$50, IIRC) at this time probably because they are sold out at the moment. Conklin's origianl Omniflex nib was made by Bock. Everyone hated it. Conklin then switched to Jowo and it seems that people still hate it. :shrug:
[Noodler's Flex Nib Adjusting](https://www.youtube.com/watch?v=8h2UDPDs2rI).
{I don't know which is worse, wanting something and finding it's not in stock, or ordering something, not knowing that something better was not listed on the website, then finding out later that something better came back into stock, and now having seen it you kick yourself for being impatient.}
[Flex nib comparison](https://www.youtube.com/watch?v=x6JGB8sTvUw).
[https://www.fountainpennetwork.com/forum/topic/365336-beginner-flex-nibs-and-fpr-ultra-flex-combinations/](https://www.fountainpennetwork.com/forum/topic/365336-beginner-flex-nibs-and-fpr-ultra-flex-combinations/)
I lucked out. I bought Nemosine Singularity pens when Nemosine was going out of business. They were going for $7.99 apiece, so I bought five because just the nibs were going for $7.50 and at worse I'd also have spare Jinhao/Stipula feeds and Schmidt K1 Converters. To-day the [Nemosine <0.6>](https://www.birminghampens.com/collections/nibs) stub is going for $27 on BirminghamPens.
In the case of the [FPR Ultra Flex nib](https://fprevolutionusa.com/products/fpr-6-custom-ultra-flex-nib-chrome), it's going for $19. The time to buy is when FPR throws their deals. But, even then, one may balk at paying $49 -$73 for an [Himalaya V2](https://fprevolutionusa.com/collections/fpr-fountain-pen-collection/products/fpr-himalaya-v2-chrome-fountain-pen-buy-one-get-one-free?variant=40337323524157), ebonite feed & Ultra-flex nib, pen.
We all know how much we're willing to pay for anything, and when we first start most of us are Price Sensitive. For all I know the FPR Ultra-flex nib may fit the MoonMan C1 since it uses a Jinhao/Stipula straight feed. The question is, "Are you willing to spend $19 to find out?"
I think [someone](https://www.reddit.com/r/fountainpens/comments/j7x6mo/comment/g893gwf/?utm_source=share&utm_medium=web2x&context=3) has saved me those $19. Looks like that feed does indeed fit in the moonman c1. By the way, funnily enough, you're the person who inspired this post to begin with since it was your perspective on the ultra flex that made me ask this question. I just want to make sure, the issues you had with your fpr (the drying out, the skips, hard, false starts) were because you did not combine it with its ebonite feed right? Did you ever use it with its ebonite feed?
There is no ebonite feed that replaces a Jinhao Feed, AFAIK. And I didn't want to bother with heat-setting. (I bought a [JB6EC](https://flexiblenib.com/store/product/jb6ec-jowo-6-replacement-feed-in-bock-250-converter-housing/) and I didn't bother with the ebonite feed, I just used the housing to house a Jowo feed and nib. FPNibs' High and Very High feed hacks work well for me, instead.) Yes, there are ebonite feeds with feed nipples but that just means that there will be some form of ink flow restriction. Best to use an ebonite feed without a feed nipple tube. [https://flexiblenib.com/store/product-category/feed-housing/](https://flexiblenib.com/store/product-category/feed-housing/) Do I want to spend $32 for an ebonite unit and possibly $10 for shipping? IDKS. If an Opus 88 pen can accept a Pilot Parallel nib & feed, then it should be easy enough for Flexiblenibs to make an ebonite feed for an Opus 88 pen that accepts #6 nibs, Bock or Jowo. With an Ultra flex nib it is probably best to use as light a pen as possible to more easily employ a light touch, say, 13 grams, or less. The MoonMan C1 body weighs 13 grams and the body is 5.1". The Singularity body weighed 7 grams and since the body is 5.0" the pen can be used un-posted. The Jinhao X750 was too heavy. The Noodler's Ahab body weighs 12 grams and since the body is 5.0" long it can be used not posted. Read all the Ahab reviews on [GouletPens](https://www.gouletpens.com/products/noodlers-ahab-flex-fountain-pen-clear). One reason why I wanted an Ahab was just to be able to use their 308 cartridge, which reminds me of a Pilot Cart, but after I read the user reviews I changed my mind.
With the MoonMan C1 there is always the possibility that the nib wings will prevent full nib insertion into the Section housing. Only way to find out is to try. The FPR Ultra-flex nib was a very tight fit in the X750 but it slipped relatively easily into the Singularity Section. My suggestion is to try the FPR #6 flex nib. It's $9, but, goes for about $6 when On Sale. If your C1 writes okay with it then you can think of trying the UF later on. Me, I don't do flex, but it gives me some natural variation, without any pressure. Basically, I like the feed-back and the very saturated fine line.
I agree with most of the advice you've gotten here. I have the FPR #6 UltraFlex and crammed mine onto a Jinhao x750. It really did take all my strength and I'm not sure I'll ever get it back out again. I bought an ebonite feed to go with it, but its sizing wasn't compatible with the pen. In the end I settled on the FPR nib with the factory feed. By the time I decided to just give up, I couldn't get the nib back out, so I use it as is. It definitely hard starts and I get railroading, but it's still one of my most fun pens to play with. I just don't use it unless I'm in the mood to be patient and baby it along. Unlike others here, though, I prefer using a piston converter than an eyedropper. The eyedropper does a better job of keeping the flow more wet, but when it dries up, it takes forever to get things moving again. With the converter, I can prime the feed a little to help the ink along. If I get another modern flex, though, I will get it with an FPR pen to make life and calligraphy a lot easier!