CGW Depressed Center Wheel, Flat, 4-1/2 in Wheel Diameter, 1/4 in Wheel Thickness, Arbor Connector, 24 Grit, Coarse Grade, Aluminum Oxide Abrasive, Wheel Type Number: Type 27, 13300 rpm Maximum, Resin Bond, Applicable Materials: Brass, Bronze, Clay Pipe, Concrete, Copper, Ductile Iron Pipe, Firing Bricks, Gray Cast Iron, Marble, Masonry, Paving Brick, Roof-Tiles, Solid Bricks, Slate and Titanium, 5/8-11 Center Hole Thread Size, Wheel Hardness: R