A single flute countersink designed for cleaning, chamfering or de-burring in alloy and non-alloy materials. Transverse hole for burr extraction High quality M2 Grade High Speed Steel (HSS) 3 flat shank to prevent slipping in the chuck" Diameter mm: 15.0: 20.0 Shank Dia. mm: 11.5 Shank Type: Three Flat Material: M2 Grade HSS Steel To Fit Screw Dia. mm: N/A Timco De-Burring Countersink (Size 15-20mm - 1 Each) in Silver