The Pocket Shark is made from a high impact polymer and features walls that are four times thicker than conventional markers. This means it's built for impact and will survive the meanest blows and roughest treatment imaginable. Plus, the screw on cap will stay in place and won't pop off like a regular marker and leak all over your clothes. Clip it to a shirt or coat pocket or carry in your purse, pack or brief case. Felt tip pen.