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. Reinforced fiberglass backing plate. Each disc balance tested for vibration-free grinding/finishing. Designed for grinding, blending, sanding and finishing on a wide range of materials.