What's the fountain pen or roller ball with the finest possible

>>2625222
For that sort of money the Platinum desk pens really are your best bets. The KDP-3000A (or DP-1000AN) is finer than the Carbon pen, probably as fine as a nib will get without tuning. It's also the cheapest gold nib you can find.
I think the Pilot Penmanship XF also comes close, but I haven't tried it myself.
Other that you won't find a true hairline nib without spending considerably more money on a #3776 UEF or Sailor Saibi-Togi.

>>2625266

yea that' what I thought; I've seen much more expensive pens that are supposedly finer but I don't want to spend that much. By chance do you know the difference between the Platinum Carbon Desk Pen Super Fine and that DP-1000AN one? The super fine is about half the price.

>>2625268
The Carbon pen has a wider feed channel for better flow with pigment ink. The normal desk pens have slightly finer nibs. Both are still finer than any western EF.

Get the Platinum Carbon, it's the thinnest line on a FP you can get at that price range. There are also the disposable Pilot pens, and the Pilot metro if you haven't looked into them already.

Either way steer clear of Western pens, they tend to have bolder nibs than Japanese pens of the same grade, and remember that at that price range you won't get much flexibility.

If you want a really, really nice and fine line check the thinner sizes of Pilot Hi-Tec, they're the most practical option IMO.

To the best of my knowledge, in that price range, the finest fountain pen is the Pilot Penmanship XF (the nib can be swapped with the Pilot Metropolitan, which only goes down to F) and the finest rollerball is the Ohto Graphic Liner 005 (0.3mm). I have both of these pens and can confirm they are great; the Ohto even has waterproof pigment ink. I haven't tried the Platinum pens that have been mentioned, but I recall reading the Penmanship was the finest available when I read through a few pen blogs and reviews before I bought one a couple years ago.

Pilot Hi-Tec-Cs (G-Tec-Cs are the western branding, and often can be found cheaper on Amazon and the like) will make the finest lines, though. They aren't waterproof, but they are Copic proof.

After trying a lot of pens, I've settled on the Pilot Precise V5 as my favorite all around pen. It will make very fine lines if you hold it vertically and gives enough variance in line weight by changing pressure and speed. A thicker line helps you work big and not get caught up in the details.