This is Pearl Abrasive's Basic Zirconia Resin Fiber Disc, It can be identified by its blue colored abrasive grain.  Fiber discs are generally used for sanding, blending, and finishing work. The premium Zirconia Abrasive grain is well suited for ferrous metals including Iron, Steel, Sheet Metals and even Stainless.  Call TAP today to get more information on Zirconia Resin Fiber Discs.