For smoothing and shaping flat or curved surfaces. Measuring 4.5" x 5.5", Sanding Sponges can be used wet or dry and are suitable for all metals, including platinum. Can be folded or trimmed to fit into tight areas. Coated on one side with aluminum oxide abrasive grains and sold in packages of 5 pieces. Grit 100 is the coarsest and grit 400 the finest. The package of assorted contains 1 each of all 5 grits.