Flap disc, blue zirconia, 40 Grit Type 29, depressed center 4-1/2 inch with 7/8 inch arbor ZA40, for right angle grinders. Cuts fast and outlast 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.