7 piece rethreading right hand, fractional, fine thread hexagonal re-threading dies set. set consists of 1/4", 5/16", 3/8", 7/16", 1/2", and 9/16" rethreading dies. for repairing damaged bolts or studs. will not crosscut or undercut the thread the way a cutting die will. do not use on hardened threads for to cut new threads. made from high carbon alloy steel for a long tool life.