Irwin Tools 1882792  SPEEDBOR Countersink Wood Drill Bit, 8-Piece Tapered drill with widened flutes for drilling fast, clean pilot holes and ensures tight fit for Adjustable four-cutter counter bore cuts and clears chips quicker for fast, smooth countersinking Counter bore attaches to flats on shank with two hex screws for a secure fit and can be adjusted 1/4 quick-change shank reduces slipping in standard chucks and is compatible with all 1/4 Adjustable stop collar attaches to counter bore with two hex screws for a secure fit and can be