PFERD Depressed Center Wheel, Series: Performance Line SG, 4-1/2 in Wheel Dia, 0.045 in Wheel Thickness, 7/8 in Center Hole, 46 Grit, Medium Grade, Aluminum Oxide Abrasive, Wheel Type Number: Type 27, 13300 rpm Maximum, Resin Bond, Applicable Materials: Cast Iron, Non-Ferrous Metals and Steel, Wheel Hardness: S, ANSI Specified Specifications Met