Perma-Coil 1/2" x 13 Stainles Steel Coarse Helical Inserts (208-108) by Thread Kits. Helically coiled inserts are made from 304 (18-8) stainless steel that has been rolled to a carefully controlled diamond shape thread form. Designed to be slightly oversized in diameter, when installed into a STI (Screw Thread Insert) tapped hole, the insert expands outward with a spring-like action that securely grips the wall of the parent material providing a much stronger, permanent thread. Perma-Coil inserts and repair kits are designed to repair stripped threads in a variety of metals including aluminum, aluminum alloys, magnesium, cast iron and bronze. Specifications: Thread Size SAE: 1/2" x 13 Drill Size SAE: 17/32" Length SAE: 0.750" Material: Stainles Steel Quantity: 6 Pieces Unit of Measure: SAE Features: Expertly crafted from high-quality raw materials Proven to deliver the longest possible wear life Designed to perform under the toughest conditions Perfect solution for professionals and do-it-yourselfers