Silicon Polishing Bullet - 220 Grit (Black) Premium silicon-carbide wheels formulated to provide the smoothest finish without the use of messy polishing compounds. This bullet is 1" x 1/4" and is grit 220 (medium). Medium, soft and flexible. For smoothing surfaces and refining edges. Operating speed range is 5000 to 12,000 rpm. Supplied as a package of a dozen.