Flap Disc Abrasive Type Coated Abrasive Material Zirconia Alumina Grade Medium Backing Plate Material Fiberglass Connector Size 5/8 In.-11 Connector Type Threaded Hole Density Rating High Flap Disc Type Type 27 Overall Diameter 4 1/2 in Series HP Backing Material Fiber Glass Backing Weight Not Applicable Coating Coverage Closed Grit 60 Maximum Operating Speed 13 300 RPM