Block sanding sponge for bare surface sanding to remove flaws or blemishes before applying initial coating. Best used on paint, wood, metal and drywall. This unique sponge channels dust away from the sanding surface and is clog resistant. Use the pattern side for detail sanding and superior conformability. Lasts 5X Longer than 3M conventional sanding sheets. Use pattern side for detail/contour sanding. Use regular side for flat sanding. Made of premium aluminum oxide mineral. Washable and reusable. Use wet or dry. For best results, sand with grain of surface and work through sequence of grits, from coarse to very fine, skipping no more than 1 grit between each sanding step.