Fiber Discs Abrasive Type Coated Abrasive Material Ceramic Backing Material Fiber Grit 50 Overall Diameter 5 in Coating Coverage Closed Resistance Properties Heat Connector Size 7/8 in Connector Type Unthreaded Hole Color Purple Features Grinding Aid to Reduce Heat and Extend Abrasive Life Rigid Backing Improves Grain Retention in the most Demanding Applications