Pitt Artist Pen: Brush Set. These artist pens are extremely fade resistant and feature waterproof, pigmented, acid-free India ink. Ideal for drawing, lettering, fashion sketches, and illustrations of all kinds. This package contains twelve Brush pens in assorted colors. These pens come in a handy slid-out storage case (6x6x 7/8"). Conforms to ASTM D4236.