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 problems. Vivid colours can be written on dark-coloured paper can be overwritten Not washable when dry Safe water-based ink with no unpleasant odour The Uni Posca PC-5M marker features a medium tip producing a 1.8 mm to 2.5 mm broad line. The width of the line depends on the writing pressure. For first-time use, please keep the cap on and shake the marker well to make the ball inside rattle. Once done, open the cap and press the marker's tip back into its body repeatedly until the ink flows into the tip. This will ensure that the marker is ready for use.