The Monument 170 has been especially designed for removing stiff backnuts from awkward placed taps & to make tap installation a more rapid process, this tool is for 1/2-inch. BSP & 3/4-inch. BSP taps. The Monument 170 tool stays in position on the tap tail so can be used with one hand & uses mechanical advantage of the thread of the tap tail to remove stiff nuts. Ideal for Monument stiffnuts 27 mm & 32 mm & for 1/2-inch BSP 27 mm nuts, 3/4-inch BSP 32 mm nuts. This MON170 is complete with 3/8-inch cordless drill adaptor & comes with full user instruction manual Monument Stiffnuts 27 mm / 32 mm. For 1/2-inch BSP 27 mm nuts; 3/4-inch. BSP 32 mm nuts. Complete with 3/8-inch. Cordless drill adaptor & full instructions.