Tapered drill bits with widened flutes for drilling fast, clean pilot holes. Adjustable 4-cutter counterbore cuts and clears chips quicker for fast, smooth countersink or counterbore drilling. Attaches and adjusts with 2 hex screws. Counterbore attaches to flat on shank for a more secure fit. Adjustable stop collar attaches to counterbore for controlling countersink depth. 1/4″ hex quick change shank reduces slipping in standard chucks and is compatible with impact drivers.