Wilson Combat Heavy-Duty Recoil Springs are made combat tough to repeatedly take a pounding yet show remarkably consistent performance every time a round is fired. Keeping a fresh recoil spring in your pistol will dramatically reduce the pounding your slide and frame receive. These enhanced, chrome silicon steel recoil springs resist taking a set even after thousands of compression cycles for improved performance and reliability over standard music wire springs. They are the top choice of competition shooters seeking the longest in spring life. Features: Full-Size 5 inches 9mm or 38 Super shooting target ammunition with a power factor of 125000 to 135000 Average service life - 20000 rounds