Pot 18 Window markers for decorating and writing on glass, windows, and virtually all non-porous surfaces including gloss finish blackboards. Not for use on traditional blackboards. To remove use a wet cloth or tissue paper. Press – tip system and 4.45mm bullet point nib. Water based assorted fluorescent colours – white, blue, purple, yellow, green and pink. (White only available in pack of 6). price shown is for one window marker.