Blue zirconia flap discs cut 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. Features reinforced fiberglass backing plate. Each disc balance tested for vibration-free grinding or finishing. Designed for grinding, blending, sanding and finishing on a wide range of materials.