The rotring rapidograph pen set, with 8 different nib sizes ranging from fine to broad, is used for drafting and drawing. - Brand: rotring - Model: rapidograph - Set Contents: 8 pens and accessories - Nib Sizes: 8 different line widths for drawing, from fine to broad: 0.2mm, 0.25mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, and 0.8mm. - Storage Case: Comes in a plastic case Based on the photos comparing the finest and broadest nibs to a 1mm ruler, I estimate the finest is for ~0.2mm lines and the broadest is for ~1mm lines. Thank you for viewing.