The Norton Surface Conditioning Disc is a 4-1/2 inch diameter x 7/8 inch thick Type 27 depressed center grinding disc made of aluminum oxide. It has a very fast cutting action for removing rust, paint, and other materials from metal surfaces. The disc attaches to a grinder, sander, or other power tool using its depressed center spindle hole. This abrasive disc is well-suited for surface conditioning of steel, stainless steel, aluminum, and other metals. It provides high stock removal and leaves a smooth finish. The disc's construction delivers long life and cool grinding.