Hero Arts-Kelly Purkey Clear Stamps. These clear stamps peel off their backing and stick to any acrylic block making for easy stamping. Simply apply your favorite ink and stamp crisp clear images! They are made from 100% photo-polymer which is latex free, phthalate free, non-toxic and biodegradable. This package contains School Planner: a set of thirty-eight clear stamps on one 6×2-1/2 inch backing sheet.