Professional tool for commercial or occasional use Twist extractors to remove broken studs, pipes, set screws, grease fittings Special reverse left handed thread sockets Impacted for strength and durability This precision kit allows you to extract hexagonal bolts which are corroded or seized and need to be removed without damaging the casing or thread Manufactured from chrome molybdenum steel for maximum durability Will easily bite into and grip the softer bolts This twist socket set is specifically designed for removing rounded nuts bolts and studs As you turn the socket anti clockwise the spiralled cutting blades grip and remove the nut or stud 1/2" drive so will fit any 1/2" drive ratchets / power bars extensions SET INCLUDES THE FOLLOWING SIZES - 17mm / 19mm / 21mm and 22mm Comes in a blow molded case for easy storage and transportation Also comes with a 12mm straight bar - total length 80mm this bar is designed for the removal of the studs or bolts if stuck in the bolts