Precision ground granite sanding block. Measures 16 1/2 x 2 3/4  x 1.25. Self adhesive sandpaper goes right on. Works great for sanding main cap, main registers, oil pump mounts, cyl head exh or intake surface, block deck or anything else that needs to be flat. I use several different ones with different grit sandpaper on each  

After you try it ......you wont be without it!!!!