MONTBLANC Montblanc refills original atom (M) - Black x2 branched into

Common nib (Nib) of Size， there are five main， from fine to coarse， respectively:

EF = XF = Extra Fine tip width of about: 0.24mm ~ 0.28mm

F = Fine tip width of about: 0.28mm ~ 0.34mm

M = Medium tip width of about: 0.34mm ~ 0.44mm

B = Broad tip width of about: 0.44mm ~ 0.54mm

BB = Double Broad tip width of about: 0.66mm ~ 0.86mm