1Application: The heavy duty M9x0.75 to 1/2?28 adapter is designed replacement for Sig Sauer 1911 22, Gsg 1911 22, 5PK 22 and some others that have M9x0.75 threads. 2Flat Ridges Design: M9x0.75 to 1/2?28 thread adapter comes with flat ridges for easy installation removal with a wrench (not included), improving the operating efficiency. 3With Thread Protector: The M9x0.75 to 1/2?28 adapter is equipped with a 1/2?28 thread protector to protect the 1/2?28 thread for use without an accessory or for storage. 4Knurl Design: The 1/2?28 thread protector is professionally designed with fine diamond knurl, looks attractive and great, and features greater friction to prevent slip. 5Durable Construction: The M9x0.75 to 1/2?28 converter with thread protector is constructed from premium high carbon steel with black oxide finish, not easy to rust, highly durable in use.