4 Pieces 4MM White Liquid Chalk Marker Pen For Non Porous Glass Windows Chalkboard Blackboard Free Dispatch From UK. Pen-Style Let You Write Clearly Without Ink Bleed-Out To Blur Lines. Easy Snap-Cap Prevents Markers From Drying Out. Environment-Friendly, Do Not Harm The Skin. It Can Be Used To Write On Chalkboard Sticker, Glass, Metal, Windows, Light Boxes, Etc. Easy To Wipe Off.