Aluminum oxide grain.A finer grit for burr-free finish., Type 1/Type 41 shape for square, burr-free cutting.Internal fiberglass reinforcement for maximum safety and controlled performance.Dual external mounting area reinforcement on 14" to 24" wheels.Special grain to fiberglass ratio provides added safety and excellent cutting performance on heavy-duty stationary saws.Cutting wheels are balanced to provide straight, even cuts.