This stainless steel adapter comes with standard 10mm x 1 to 1/2x28 threads for use with the FN FiveseveN handgun and a 22Sparrow, Spectre II or any other 1/2x28 threaded .22 LR suppressor. Enjoy the benefits of O-ring engagement, which keeps the muzzle threads clean and your suppressor from loosening while firing. The FN 10mm x 1 to 1/2x28 Adapter comes with thread protector, which also has O-ring engagement.