These water-proof, Silicon Carbide, 7/8" diameter, medium discs are manufactured with on a paper backing which has a water-proof front. (This silicon carbide is a natural mineral; slightly less aggressive than white aluminum oxide. Recommended for general use.) Since they are manufactured with the Moore Snap-on brass center, they need to be used with a Snap-on mandrel (sold separately). Max. operating speed: 30,000rpm. Sold in box of 200 discs. Made in USA