Fiber Disc, Abrasive Type Coated, Abrasive Material Aluminum Oxide, Backing Material Fiber, Backing Weight Not Applicable, Grit 50, Overall Diameter 4 in, Series 381C, Coating Coverage Closed, Maximum Operating Speed 15,000 RPM, Connector Size 7/8 in, Connector Type Unthreaded Hole, Color Brown, Grade Coarse