This TCT countersink clamps onto any drill between 3.0mm and 7.2mm in diameter. |Recommended for wood and man-made boards|By reversing the countersink on the drill, it can be used as a non-cutting depth stop. |Ensure flutes of drill are aligned with flutes of countersink.|Do not overtighten screw.|Not suitable for production applications and not suitable for ferrous and non-ferrous metals.