Uni Posca markers are famous for the ability to write or draw on any surface including paper, photos, plastic, metal, glass and wood. They feature vivid, opaque ink which is water-based, lightfast, waterproof and non-toxic. The ink is removable on nonporous surfaces like glass but will be permanent on porous surfaces like paper. They show up well on both light and dark surfaces. After drying, you can cover it with another Posca marker without any problems. Vivid colors and can be written on dark colored paper can be overwritten Not washable when dry Safe water-based ink with no unpleasant odor The Uni Posca PC-5M marker features a medium tip producing a 1.8 mm to 2.5 mm wide line. The width of the line depends on writing pressure.