Sanding discs are used for grinding, deburring, blending, cleaning, finishing, and polishing a wide variety of materials. Discs can be backed with fiber resin, cloth, paper, or film. Fiber resin- and cloth-backed discs are very durable for heavy-duty use, while paper-backed discs are more flexible and economical. Film-backed discs are best for fine finishing work. Disc attachment type can be arbor/shank, hook and loop, PSA, or quick change. PSA and hook and loop systems are used for lighter-duty deburring, blending, medium stock removal, and finishing, with quick change systems being better suited for heavier work. Common abrasive materials include aluminum oxide, alumina zirconia, ceramic, silicon carbide, and diamond. Disc grades can vary from very coarse to ultrafine, with corresponding grit numbers. Some paper- and film-backed discs are available as a continuous disc roll.