Irwin Tools 1882786 SPEEDBOR Countersink Wood Drill Bit, Number-4 Replacement Bit;

IRWIN Wood Countersinks feature a tapered drill and wide flutes that drill fast, clean pilot holes and ensure a tight fit for screws. They have an adjustable four-cutter counter bore attachment that cuts fast and clears chips quickly for fast, smooth countersinking applications. The counter bore feature attaches flats on shank with two hex screws for a secure fit and can be adjusted for controlled pilot hole depth. IRWIN SPEEDBOR countersink bits fit all standard 1/4" quick-change chucks, including impact drills.