Plastic backing greatly increases the service life of sanding discs, and now they’re available in a new range. Aluminum oxide grit is applied to a plastic disc (genuine 3M aluminum oxide film) and mounted on brass centers. Use with miniature mandrel no. 214-313. Maximum speed: 30,000 RPM. Packs of 100 discs, all 7/8” (22.2 mm) in diameter. Made in USA.