Depressed Center Wheels, Abrasive Wheel Type Type 27, Abrasive Wheel Diameter 9 in, Thickness 0.25 in, Arbor Hole Size 5/8 In.-11, Abrasive Material Aluminum Oxide, Abrasive Grit 24, Max. RPM 6,600 RPM, Series Gemini XXL, Grade Extra Coarse, Application Ferrous Metal, Gray Iron, Stainless