Cup Brush, Cup Brush, Bristle Type Knotted Wire, Brush Dia. 3 1/2 in, Mounting Type Arbor Hole, Arbor Hole Size 5/8 In.-11, Abrasive Shank Size No Shank, Wire Dia. 0.02 in, Bristle Trim Length 7/8 in, Abrasive Material Carbon Steel, Max. RPM 13,000 RPM