Depressed Center Wheels, Abrasive Wheel Type Type 27, Abrasive Wheel Diameter 5 in, Thickness 0.25 in, Arbor Hole Size 7/8 in, Abrasive Material Aluminum Oxide, Abrasive Grit 24, Max. RPM 12,225 RPM, Series Norton Metal, Grade Extra Coarse, Application Ferrous Metal, Gray Iron, Stainless