7/8" Silicon Polishing Wheel (Knife Edge) - 220 Grit, box of 100 Premium silicon-carbide wheels formulated to provide the smoothest finish without the use of messy polishing compounds. This wheel is 7/8" and is grit 220 (medium). Edge is knife. Medium, soft and flexible. For smoothing surfaces and refining edges. Operating speed range is 5000 to 12,000 rpm.