The SI Barrel Thread Protector is a machined aluminum thread protector that adds a degree of customization and aesthetics to protect your crown and threads. Whether you are still deciding on a compensator device for your custom pistol, protecting the fine threading of a supressed barrel, or simply transporting or storage, The SI Pistol Barrel Thread Protector performs a valuable function without sacrificing the looks. All the thread protectors are A 1/2 x 28 tpi. Mfg: Strike Industries SPECS: 1/2 x 28 tpi