#10 wood countersink, tapered drill features widened flutes for drilling fast, clean pilot holes, 4 cutter, adjustable counter bore cuts & clears chips for fast, smooth countsinking, counter bore attaches securely to the flats on the shank with hex screws & adjusts for controlled pilot hole depth, 1/4 quick change shank reduces slipping in standard chucks, compatible with all 1/4 quick change chucks including impact drills, use for fine woodworking projects, bit diameter 3/16, counter bore size 7/16, plug size 7/16, shank size 1/4.