CGW® depressed center wheel, 4-1/2 in wheel dia, 5/8-11 center hole, 24 grit, coarse grade, D3 diamond abrasive, 13,300 RPM maximum, applicable materials: alloy steel, ceramic, ductile materials, hard face metal alloy, mild steel and stainless steel, wheel type number: type 29. CGW® 70401 Depressed Center Wheel, 4-1/2 in dia, 5/8-11 Center Hole, 24 Grit, Diamond Abrasive