Depressed Center Wheels, Abrasive Wheel Type Type 29, Abrasive Wheel Diameter 4 1/2 in, Thickness 0.125 in, Arbor Hole Size 7/8 in, Abrasive Material Aluminum Oxide, Abrasive Grit 36, Max. RPM 13,580 RPM, Series Gemini Flexible, Grade Extra Coarse, Application Ferrous Metal, Gray Iron, Stainless