The Faber-Castell PITT Artist Drawing Pens are an excellent tool for any application requiring permanence and precision. They contain a highly lightfast, pigmented ink that is smudge and waterproof when dry. The ink in these pens is acid free and pH neutral for archival permanence. The three different nib sizes M (Medium), F (Fine) and S (Super-Fine) offer a range of expressive fixed line widths. The Brush Pen (B) offers an organic variable line width. These pens are perfect for sketching, cartooning, fine ink drawings, and journals.