They are designed to drill and coutersink simultaneously, a wide variety of materials. Supplied with a HSS slow spiral drill bit. Fully adjustable, a hex key is supplied. Use at drilling speeds only. Not suitable for ferrous or non ferrous metals. Please ensure drill flutes are aligned with flutes of countersink. For replacement Twist Drills, use slow spiral type e.g. Refs 501/18 to 501/716. Specifications • Dia Metric: 15.9 • Dia Imperial: 5/8 • Dia2 Metric: 5.55 • Overall Length Metric: 90