This is a EAG1020320 9x11x320 Waterproof Paper. This is a Eagle Abrasives Silicone Carbide Flexible Back Waterproof Sheet. The world's most reputable wet sanding paper for it's durability, speed & extremely uniform abrasive grains. Sharp silicone carbide abrasive grain is resin-over-resin bonded on a highly flexible anti-slip backing which requires no pre-soaking before sanding.