Silicon Polishing Cone - 220 Grit (Black) Premium silicon-carbide wheels formulated to provide the smoothest finish without the use of messy polishing compounds. Cone is mounted on 3/32" shank. This cone is 5/8" x 7/32" and is grit 220 (medium). Medium, soft and flexible for smoothing surfaces and refining edges. Operating speed range is 5000 to 10,000 rpm. Supplied as a package of a dozen.