4 Pcs set includes bits for drilling pilot holes for screw sizes #6，#10，#13 ，#16.Function: can drill the screw holes and keep on the same axis， after screw in screw£¬nut below the board!Apply to with a clamp or joint drilling machine， suitable for drilling in the hard wood and wood floor， machine screw for wood screw.Material: HSS Drill 4241.Black chamfer drill body material: steel 45.Shank: 2.5mm dia hex shank.Model/The corresponding bit size:#6: 3mm#10: 3.5mm#13: 4mm#16: 4.5mmPackage includes:4 x drill bits