Premium Quality With high-frequency quenching for heat treatment, the HSS countersink bits have high hardness and toughness. Coated by titanium, the chamfer cutter kit is rustproof and has a long service life. 6 DIFFERENT SIZES . Variety of specifications: 6mm ( 1/4 inch ), 8mm ( 5/16 inch ), 9mm ( 3/8 inch ), 12mm ( 1/2 inch ), 16mm ( 5/8 inch ), 19mm ( 3/4 inch ) Eliminates Chatter&VibrationAll sharp corners have a 90 angle for accurate counter holes. Five-blade Chamfering with a groove, easier to discharge debris. Five-flute design reduces vibration for smoother drilling. Great Design Standard 1/4" hex bit helps a quick drill and makes dont slip in drill chucks. There're numbers on the corresponding countersink hole cutters, so it's convenient for you to pick out the one you need quickly Widely Used. The chamfering drill bits with 5 flutes are mainly used for wood openings, reaming, chamfering, screw head and so on. Also applies to wooden planks, fiberboard, particle board, plywood, plastic, alumiumn board , pcb board and more