The Glass Pen formula is specifically designed for use on glass and mirrors. Its water-based ink comes in ten very opaque colours which are easily removed from the surface with a damp cloth or for more convenience Rainbow Glass Cleaner.Product Specifications• 5mm Bullet Nib Reversible.• Wet wipe erase with a damp cloth or Rainbow Cleaner.• Suitable for indoor and outdoor use.• Resistant to light showers.• Valve activated to control ink flow.• For use on glass, windows, and mirrors.• Water based & non - toxic.