Combination aluminum oxide and silicon carbide formulation.Use the Ductile??????????wheel for extra hard metals, hydraulic hose and PVC pipe.Heavy Duty Wheels: Designed with greater amounts of reinforcement for use on high-speed powered saws., Type 1/Type 41 shape for square, burr-free cutting.Wheels are constructed with the highest quality fiberglass to withstand the toughest applications.Available in multiple arbor sizes to fit a wide variety of tools.