Metabo® Depressed Center Wheel, General Purpose, Series: Original Grinding®, 4-1/2 in Wheel dia, 1/4 in Wheel Thickness, Threaded Connector, A24N Grit, Aluminum Oxide Abrasive, Wheel Type Number: Type 27, 13300 rpm Maximum, Resin Bond, Applicable Materials: Steel and Ferrous Metals, 5/8-11 Center Hole Thread Size, Wheel Hardness: N, Black Wheel, Yes Reinforced. The quality of cutting and grinding wheels depends on several factors - the grain (size, shape and quality) determines how aggressive a wheel is. The right mix of bonding resins, additives and fiberglass reinforcement determines the wheel life. Metabo® cutting and grinding wheels are designed and manufactured in accordance with our most stringent specifications so that they, in combination with our power tools, achieve the best performance and productivity, saving time and money. Metabo® 655726000 Original Grinding® General Purpose Depressed Center Wheel with Hub, 4-1/2 in dia x 1/4 in Thick, A24N Grit, Aluminum Oxide Abrasive