Perma-Grit Double sided sanding block This sanding block from Perma-Grit uses tungsten carbide sanding paper on a lightweight, hollow metal frame. It has coarse grit one side and fine grit on the opposite side and is able to sand perfectly at 90 degrees when placed on its side. Overall length 140mm x 51mm. Coarse grain grit: 180 (USA 60); fine grain grit: 320 (USA 120).