Strike Industries Recoil Spring for Glock pistols allows you to fine tune the timing and recoil. Constructed and wound from 17-7ph stainless steel flat wire, the recoil spring is for reliability and longevity. This recoil spring is 13 lbs. The SI recoil spring for Glock pistols allows one to fine tune the timing and recoil characteristics of their Glock firearm. While the factory springs do work reliably with most ammunition, they do leave some things to be desired when it comes to handling characteristics, and they wear out over time requiring replacement. The reduced power springs also work great with lightened slides. Tune your Glock pistol for greater reliability and speed up follow up shots with an SI recoil spring. Features: Wound from flat wire for reliability and longevity 17-7PH stainless steel resists corrosion and lasts much longer than factory carbon steel springs