5 piece drill countersink set. Heat treated tool steel countersinks with a HSS drill. Adjustable for different length screws and can produce a 9.5mm (3/8 inch) diameter or 12.7 mm (1/2 inch diameter counterbored hole for woodplugs. The drill produce pilot holes only. Shank Diameter=1/4 inch hex. Includes 1 x 2.0mm (5/64in) drill countersink|1 x 2.5mm (3/32in) drill countersink|1 x 2.75mm (7/64in) drill countersink|1 x 3.25mm (1/8in) drill countersink|1 x 3.5mm (9/64in) drill countersink