Continuing the discussion from 3D printed fountain pens and feeds:
In another thread, fountain pen nibs were brought up.
Fountain pen nibs come in multiple sizes, generally running from extra fine to broad. In between, there’s generally fine and medium.
The nib size normally determines the line width. Extra fine puts out a thinner line than a broad nib.
Japanese nibs (like Pilot and Platinum) extra fine and fine nibs generally are thinner than the western equivalents (like Lamy and others) because Japanese character writing can require very thin lines.
Flex nibs can create more width variation by the tines spreading under pressure to put more ink on the page.
Here’s some information about flex nibs.
(at 35:35)
What is your preferred size of nib?