Forney 2 in coarse wire cup brush. It's the ideal cup brush for light duty cleaning action. Typical applications include removal of dirt, rust, paint, scale, and weld spatter. Designed to be used on portable 1/4 in diameter electric or airtools, or common cordless drills. High carbon steel, Coarse, Shank: 1/4 in (6.35 millimeters), Maximum Revolutions Per Minute (RPM): 6,000.