Tiger® Depressed Center Wheel, Contaminant-Free Non-Loading Performance Line, 9 in Wheel dia, 1/4 in Wheel Thickness, Hub Connector, 24 Grit, Coarse Grade, Silicon Carbide/Aluminum Oxide Abrasive, Wheel Type Number: Type 27, 6600 rpm Maximum, Resin Bond, Applicable Materials: Aluminum, 5/8-11 Center Hole Thread Size, Wheel Hardness: R, Yes Reinforced.Fabricators know aluminum can be a challenging metal to work with because of its low melting temperature and tendency to load and stop cutting. That's why Weiler designed a new line of cutting and grinding wheels that deliver a non-loading solution that maximizes cut rates, increasing productivity when working with aluminum. These wheels leverage a unique blend of abrasive grains and contaminant free additives that work to prevent loading, resulting in higher cut rates and long wheel life. Weiler® 58234 Tiger® Contaminant-Free Non-Loading Performance Line Depressed Center Grinding Wheel, 24 Grit