4-inch Diamond Cup Grinding Wheel Single Row Grit 30~40, For Concrete 4 inch Single Row Diamond Grinding Cup Wheel for Heavy Material Removal For grinding marble, tile, concrete and rock. Diameter: 4 inch; Arbor: 5/8-11 Diamond Grit: 30~40, Base Material: HCS Steel 65Mn For Dry and Wet use, (Wet use recommended)