Depressed Center Grinding Wheel Abrasive Material Zirconia Alumina Connector Size 7/8 in Connector Type Unthreaded Hole Grit 30 Overall Diameter 4 1/2 in Overall Thickness 0.25 in Primary Material Applicationn Steel Compatible Tool Type Angle Grinder Series SG Wheel Type Type 27 Maximum Operating Speed 13 300 RPM Grade Extra Coarse