SOFTBACK SANDING SPONGES provide flexibility and conformability to allow for sanding b hand in areas inacessible to machine sanding. They feature aluminum oxide mineral coating on a foam pad with a waterproof bonding system.Can be used either wet or dry when sanding on wood,fiberglass/gelcoat,marine paints,metals and plastic. 41/2"x51/2". Description:superfine Grit:1500-600