KATO Perma-Coil Insert Pack includes stainless steel inserts used to repair stripped threads in all types of materials. Unlike threaded solid bushing type fasteners, Perma-Coil (tanged) inserts provide space and weight saving to your repair process. In addition, Perma-Coil (tanged) inserts eliminate the need for oversized drilling and tapping, welding, or plugging of damaged holes.