MILWAUKEE 4MM - 12MM SHOCKWAVE IMPACT DUTY STEP DRILL BIT. Shockwave Impact Duty™ step drills are designed to be used with impact drivers.The 1/4" hex shank has an optimised SHOCKZONE™ body which ensures most durability by reducing early shank breaks.Dual spiral flute: optimised for impact drivers and for smooth drilling.Titanium Aluminum Nitride (TiAIN) coating for 5x more life vs. standard non impact rated step drills when used in an impact driver.Rapid Strike™ tip: quick and more accurate start without walking. Also less heat generation for longer life.Laser engraved markings: Do not wear away with time.Milwaukee accessory code number : 48899262Genuine Milwaukee accessories.