This flat wire recoil spring for 1911s fits commander guns with full length, 1/4" diameter guide rods. We also use this spring in our Springfield® 4.0" 9mm kit. The 14lb spring weight is perfect for use in 9mm 1911s. ISMI Springs are typically made from silicone chrome instead of 150 year old music wire. Every ISMI spring is heat treated, shot peened & stress relieved to enhance durability, consistency and reliability. Our springs are made for us by ISMI. ISMI is a contractor of the U.S. government and produces springs used in machine guns with incredibly high cycling rates. Also, the creator of ISMI springs obtained his knowledge from extensive research in the development of springs used in Indy car racing.
**This spring will NOT work with standard diameter spring guides or guide rods!