Flap disc, blue zirconia, 36 Grit Type 27, depressed center 4-1/2 inch with 7/8 inch arbor ZA36, for right angle grinders. Cuts fast and outlast sanding discs 10-to-1. 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 or finishing.