Featuring Pilot's special CSP (Controlled Surface Properties) ink, this pen offers a great balance of the most important features of a permanent marker. The oil-based ink is vivid, fast drying, water resistant, fade resistant, and low odor. It writes well on a variety of surfaces including paper, plastic, and glass, and it resists rubbing off even on non-porous surfaces. And thanks to a special membrane covering the tip, the pen won't dry out even if the cap is left off for 24 hours.