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 with a 7/8 inch arbor hole and maximum operating speed of 13,300 RPM. It is well suited for surface conditioning of steel, stainless steel, aluminum, and other metals. This made in the USA abrasive disc helps prepare surfaces for painting or welding.