These Foredom AK5690 Ceramic Purple PSA Sanding Discs are from 3M. They are excellent for sanding and finishing wood, metals, fiberglass, diestone, plastics, and other materials. 3Ms Cubitron ceramic aluminum oxide mineral sharpens itself with use. Once initial grinding wears the grain flat, it fractures along micro cracks creating new cutting edges. This process repeats itself throughout the entire grinding process. These sanding discs have a 2 to 4 times longer abrasive life than traditional aluminum oxide bands and discs with faster stock removal with less heat and loading. This pack contains 1 disc each of 60, 80, 120, and 220 grit. Discs are 3". Made in the USA.