3M(TM) SandBlaster(TM) Bare Surfaces Sanding Sponges, 20917-80, Med 80, Sleeved, 12 Per Case. 3M(TM) SandBlaster(TM) Bare Surfaces Sanding Sponge is ideal for sanding bare surfaces, such as wood, metal and drywall. Use it to remove flaws ion wood before applying the first coating. Recommended for round or highly contoured surfaces. 3M(TM) SandBlaster(TM) medium sanding sponges sand fast, last long and are clog resistant.