4-1/2" x 7/8", 36 Grit Zirconia Flap Disc, Zirconia Grit Enables 3 Times Faster Material Removal Than Fiber Resin Metal Sanding Discs, The Abrasive Cloth Provides Up To 15 Times Longer Life, Fiberglass Backing Provides Optimal Grinding Angle Of 10 To 25 Degree.