Pro-Thread Kits offer a cost effective method of repairing and strengthening threads in various materials such as cast iron, steel, aluminum, and other metals and plastics. Effective for automotive repair, spark plug ports, outdoor power equipment, motorcycle repairs, farm equipment, and more! Easy to install, just DRILL, TAP, INSERT, SNAP! Pro-Thread inserts provide a permanent wear resistant internal thread. Stainless steel inserts resist the effects of temperature and corrosion. Wire inserts help to compensate for the thread and pitch angle errors Repaired threads are generally stronger than the original parent material thread. Thread size: 5/8" - 11 UNC. Replacement Inserts: #23119.