Junlai 630 Ivory Piston Fountain Pen: Size #8 (EF/F/M/B/B Stub/Architect Nib)
B Stub nib is grounded nib, The writing thickness of nibs are 0.7-1mm. 1 mm is the thickest thickness, which is the thickness for vertical writing. However, in the actual writing process, you cannot only write vertically.