What do the different nib sizes mean?
Nibs are rated several ways: the size of the nib itself, the size of the point (actually the width of the line it leaves), the orientation of the point, and the flexibility of the nib. The physical size and shape of the nib affect the nib’s flexibility and how well it writes. However, nibs are typically rated by their tip size, and tips are produced in several sizes: extra fine, fine, medium, and broad. There are, of course, additional variations in each manufacturer’s product line, but those are the general sizes available almost everywhere. Be careful on tip sizes: one pen manufacturer’s “fine” tip may leave a narrower or wider line than the “fine” tip from a different manufacturer. For that matter, two pens from the same manufacturer with the same tip size might leave considerably different looking lines! For example, a fine tip may leave a line no wider than a single hair, and a medium tip might leave a line as wide as, maybe 5 of those same hairs. A broad might leave a line as wid