3M™ Aluminum Oxide Sandpaper 9002NA, 9 in x 11 in, Medium grit. 3M™ sandpaper comes in a variety of minerals and a wide grit range. This medium-grit aluminum oxide sandpaper is a general purpose abrasive that can be used on painted surfaces, bare wood, and metal. The 9 in x 11 in sheets can be cut to size to use by hand, on a sanding block, or a power tool sander. Sanding is an integral step in preparing a surface to receive a coating. For the best sanding results, sand with the grain of the wood and work through a sequence of grits, from coarse to very fine.