The Cutterpillar tempered safety glass add-on mat complements CutterPillar Glow Boards for when you need a harder surface than the standard self-healing mat. Tempered glass is 20 times harder than regular glass. Perfect for working with glues, fusibles and paints. Features 1/2" and 1/4" grid system with commonly used angles. Imperial and metric rulers Scratch resistant Washable