Edding 141 F/4s Four-color permanent pen set, 0.6 mm: A fine nib is needed for fine letters or marks or when space is limited. For fine permanent writing on almost any non-porous plastic surface, use a permanent pen. Alcohol can be used to correct writing. The stroke width of the round nib is 0.6 mm. The permanent pen ink dries quickly and is waterproof. Decide on colors