These Sand-O-Flex refills feature Merit’s 350-RP aluminum oxide abrasive with a resin bond. The Sand-O-Flex Wheel (sold separately) is 6-1/2” diameter overall with a 4” diameter high-impact plastic body and a 1/4” diameter steel shank. With firm cushioning brushes (replacement brushes sold separately) Sand-O-Flex’s abrasive strips are forced into around and over corners hollow and fluted surfaces and small openings. Pressure is distributed evenly over the surface to prevent loss of detail and the flattening of rounded areas for sanding metal wood plastic rubber and ceramic. Package of 10.