Fiber Disc Abrasive Type Coated Abrasive Material Ceramic Backing Material Fiber Grit 36 Overall Diameter 5 in Series RazorStar F990S Maximum Operating Speed 13 000 RPM Resistance Properties Tear Features A Single Discs Design has been Optimized for Superior Performance on all Materials Including Carbon Steel Aluminum Stainless Steel and Hard-to-Grind Metals Engineered Shaped Ceramic Grain are a Breakthrough Technology Specifically Designed to Deliver Unbeatable Grinding Performance