Wilson Combat's 11 lb. recoil spring full size 5" 9mm or .38 Super shooting target ammunition with a power factor of 125,000 to 135,000 (Velocity x Bullet Weight = Power Factor) Average service life 20,000 Rounds. *Note- this is the standard recoil spring we install in our full-size 9mm pistols. 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.