FlexOvit® Metalhog® Depressed Center Grinding Wheel, Rapid Grind, 4-1/2 in Wheel dia, 1/4 in Wheel Thickness, 7/8 in Center Hole, Arbor Connector, AXT24S Grit, Coarse Grade, Aluminum Oxide Abrasive, Wheel Type Number: Type 27, 13300 RPM Maximum, Resin Bond, Applicable Materials: Metal and Stainless Steel, Wheel Hardness: S, Specifications Met: ANSI B7.1. FlexOvit® Metalhog® A1230 Rapid Grind Depressed Center Grinding Wheel, 4-1/2 in dia x 1/4 in Thick, 7/8 in Center Hole, AXT24S Grit