Preamer 4Pcs Hex Shank Countersink Drill Bit Set for Wood, 6#8#10#12 Screw Size Make drilling, countersinking and couterboring a one-step process 1/4" hex shank can be used with power drills and quick change chucks The adjustable stop collar allows you to either set the screw head flush with the surface or drill a Countersinks will drill the pilot hole and countersink or counter-bore for screws in one step. Countersink to drive the head of the screw flush with or slightly below the surface Size : In the picture.Material of Drill Bit:HSS 4241