The Bosch HD21-2 2-speed hammer drill features a torque control auxiliary handle. This securely locks into place for maximum control in heavy duty drilling applications. It has a 2-speed gear box. This allows the user to match the speed to the application. This gives you either the power or precision necessary. 1/2 in. 3-Jaw Chuck for rugged hammer drilling applications. Dual-mode Selector easily converts from rotation only to hammer drill mode. Patented rotating brush plate provides equal power in reverse to easily back out bound-up bits and doubles brush life. Integral Slip Clutch helps minimize torque reaction.