Faber-Castell Pitt artist pens contain highly pigmented water-based India ink that is permanent and waterproof once dry. They do not bleed through paper, and the ink is lightfast, odorless and archival. Pitt pens may be used on any porous surface like paper, canvas and wood, for drawings, sketches, layouts, fashion design, illustration and more. The range of nib sizes availble make the Pitt an extremely versatile pen, and very popular for mixed media work. The Pitt Brush pen is available in 60 colors. The flexible nib creates a line from 1mm to 5mm, depending upon pressure and placement on the surface.