The thickness of the nib varies. Generally, the most common pen tip sizes are B (width), M (medium), FM (fine-medium), F (fine) and EF (extra fine), with B > from coarse to fine; M>F> ef.
The size of the nib is slightly different from pen factory to pen factory. Under the same size unit, the Japanese pen will be thinner than the European pen.
According to the usual writing habits, westerners usually use the M-tip as the main pen and choose the B-tip when signing. Due to the complexity of Chinese writing strokes, F or thinner EF pen tips can generally be used.
Extended data
There are five common pen tip sizes, from thin to thick:
1, EF = XF = the width of the ultra-fine nib is about 0.24 mm ~ 0.28 mm ..
2. F = F = the width of the fine pen tip is about 0.28 mm ~ 0.34 mm
3.M = M = the width of the medium pen tip is about 0.34 mm ~ 0.44 mm
4.B = width b = wide nib: 0.44 mm ~ 0.54 mm
5.BB = the width of the double-width pen tip is about 0.66mm ~ 0.86mm. ..
There are more subdivided pen tips, such as EEF with thinner EF, 3B with thicker BB (triple width) and MF pen tip between F and M. Although different brands have different definitions of pen tip size (that is, M pen tip of M brand is thicker or thinner than P brand), the width of pen tip is mostly between 0.18 mm-0.86 mm. ..
In order to meet personal writing preferences, some manufacturers will also have inclined nib, such as: om = ob = Ob = Ob = Ob = Ob.
Baidu encyclopedia-pen
Baidu encyclopedia-nib