PFERD Replacement drive arbor is designed for mounting disc brushes. Brush mounts between a single washer and the flat head. Locked in place with a reverse threaded nut. Allows the brush to be close to the work piece. Threaded shoulder. Specification: Fits Arbor Hole (inches): 1/2, 5/8; Shank Diameter (inches): 1/4; Clamping Width (inches): 1/8 - 1/2; Flange Diameter (inches): 15/16; Arbor Style: Flat; Overall Length (inches): 1-7/8; Maximum Rotational Speed (RPM): 25,000.