4", 80 Grit, Blue Zirconia, Type 29, Flap Disc, Depressed Center, 5/8" Arbor, For Right Angle Grinders, Cuts Fast & Outlasts Sanding Discs 10 To 1, Great Flexibility, Ideal For Rough Or Fine Finishing, Multiple Layers Of Zirconia Cloth Flaps Constantly Exposing New Extra Sharp Grinding Points, Laminated By State Of The Art Automated Equipment, Reinforced Fiberglass Backing Plate, Each Disc Balance Tested For Vibration Free Grinding/Finishing.