Irwin Tools 1882784  SPEEDBOR Countersink Wood Drill Bit, Number-12 #12 wood Countersink This product is highly durable This product is manufactured in China Tapered drill with widened flutes for drilling fast, clean pilot holes and ensures tight fit for screws 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 for controlled pilot hole depth 1/4" quick-change shank reduces slipping in standard chucks and is compatible with all 1/4" quick-change chucks, including impact drills