"C" Countersinks - Used to countersink and counterbore for the heads of screws in woods, plastics, and non-ferrous materials. Made of Carbon Steel and heat-treated for long tool life. The Type "C" countersink is designed for use in all woods, plastics, and non- ferrous metals. The countersink is held in place with 2 hex socket set screws fastened into the flutes of the drill. This countersink can be mounted on taper point, brad point and regular point drills.