Heat treated tool steel countersink with a HSS drill. Adjustable for different length screws and can produce a 9.5mm (3/8 inch) diameter counterbored hole for woodplugs. The drill produce pilot holes only. D=3/8 inch D=9.5 mm D2=5/64 inch D2=2 mm Shank Diameter=1/4 inch hex Screw size S/W=n.a H/W=No. 4