Specially designed Chrome Molybdenum spring steel flexes at preset torque ratings. Allows accurate application of specific torque to automobile wheel fasteners. Prevents over-tightening or uneven tightening of lug nuts, a major cause of wheel and brake rotor damage 5 extensions cover most passenger and light truck / SUV wheels. For use with 1/2" drive impact wrenches rated at 250 ft/lbs and line pressure of 90 110 PSI. For aluminum and chrome wheels, use with JETs 1/2" drive Mag Wheel Power Sockets. Blow mould case with removable lid.