Professional tool for commercial or occasional use -Designed to remove difficult threaded studs or install them -Suitable for removing broken or seized bolts and studs -Tool is designed to remove difficult threaded studs or install them -Knurled roller users cam action to grasp stud firmly and minimizes damage. -Cam rotates to grip onto the stud for quick and easy use -Suitable for a range of heads including - head studs, main studs and carburettor studs -To be used with a 1/2" drive ratchet -Suitable for studs from 1/4" (6mm) to 3/4" (19mm)