Wire Helicoil Key Locking Thread Inserts The bolt socket is a special fastener with threads inside and outside, and 4 or 2 bolt keys (below M6) on the outer thread. The Keylocking Insert is mainly used in military industry, aerospace, railway locomotives, vibration machinery and other products that require high thread strength. From the appearance of the product, the bolt sleeve can be divided into thin-wall type and heavy-duty type. Stainless Steel Threaded Inserts are also reinforced and extra-heavy types. The most basic function of the bolt sleeve is to repair the internal thread and strengthen the external thread. As a thread repair method, the bolt sleeve can quickly and effectively repair damaged threads; when used on low-strength materials, Stainless Steel Insert can greatly enhance the strength of the threaded hole. Size& Type: Metric: Lightweight(Miniature): M3 to M12 (Other sizes on request) Heavy Duty(Extra Heavy Duty): M4 to M20 (O…