Lapping film sheets are used for very fine finishing on plastic, fiberglass, wood, and metal. They are formed by binding an abrasive grain to a polyester backing and can be used wet or dry. Some sheets have a hook and loop or PSA attachment type. Common abrasive materials include aluminum oxide, silicon carbide, silicon dioxide, and diamond. Abrasive grades, and corresponding grits are very fine to ultrafine for microabrasion. Lapping film rolls are a continuous length of abrasive sheets that can be cut to custom sizes.