4090 Jumbo Chalk Markers are for non-permanent opaque designing, decorating and writing on non-porous surfaces, such as windows, dark boards, glass, plexiglass and mirrors. The water-based liquid chalk with a neutral smell can be wiped off virtually all non-porous surfaces with a damp cloth. Unlike standard chalk, your hands will not get dirty. Pump system: shake before use, remove cap and pump. The chisel nib has a stroke width of 4-15mm. Neon colors become visible and luminous under UV light. Cap can be stored on the end of the barrel to prevent risk of losing it.