8" x 3" Expanding Drums: the best way to obtain smooth, highly polished stones. The soft, pliable rubber expands during rotation to grip the sanding or polishing belts. Changes are made quickly and easily by sliding the belts from the drum. At low speed, the flexible surface wraps around curved surfaces for increased contact with the work piece. When used at high speed, the drum surface acts like a hard rubber grinding wheel. Use with diamond or silicon carbide belts. The heavy machined hubs are supplied with bushings to fit 1”, 3/4”, 5/8” and 1/2” arbors.