4-1/2" Diameter, 7/8 Inch Arbor, Type #27, 13300RPM maximum speed. Premium resin-bonded aluminum oxide abrasive with high performance: durable, good abrasion resistance, anti-static and anti-clogging. Made from aluminum oxide, designed for high speed sanding and heavy duty removal. Delivering fast and long lasting cut. Aluminum oxide flap disc features high performance.