For use on conventional slate chalk board and glass, these Pentel Markers contain liquid chalk, which removes easily with a wet cloth. Suitable for both indoor and outdoor use, the markers feature a valve action for a smooth, controlled ink flow. Ideal for displays, decorations, menus, information and more, the chisel tip writes a variable line width of 1.5-4.0mm. This assorted pack of 4 chalk markers contains red, yellow, blue and white.