MAGBIT 909.3616 MAG 909 2-1/4-Inch Counter Shark Cuts 2-1/4-Inch counterbore to accommodate washer and bolt head below surface of wood Six super sharp teeth on outer diameter to cut clean hole and leave smooth finish Securely attaches to a bit with a heavy duty set screw. Designed to work with Magbit counterbore drills and 357DLX,303DLX,715 and 735 style auger bits with a diameter of 5/8-Inch or larger For use in all types of wood