Silicon carbide grain.Long life.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.Special silicon carbide grain formula provides excellent cutting action on masonry, concrete, stone and aggregate.Available in multiple arbor sizes to fit a wide variety of tools.