PFERD M-BRAD Abrasive filament cup brush is designed for use on hand-held right-angle tools or stationary machine spindles. Ideal for flat surfaces with numerous holes and low projections. Cup brushes are especially effective on aluminum, cast iron, brass, copper and hardened steels. Recommendation for use Suitable tool drives: stationary machines, variable speed angle grinders. Diameter (inches): 4; 5/8-11 Thread; Wire Size: .040; Filament Material: Nylon / Silicon Carbide; Maximum Rotational Speed (RPM): 6000; Trim Length (inches): 1-1/2; Recommended RPM: 1,200 - 4,000.