7-inch Velcro Backer pad works with our 7" Pool Plaster Disc. Works well with all variable speed polisher and sanders. The pad has a 5/8-inch rubber pad adhered to a hook and loop material with 5/8-11 thread for a polisher, or sander. The backer pad provides our non-corrosive pool plaster diamond disc with pool plaster sanding disc a 100% contact with flat pool plaster surfaces. Maximum RPM 3000.