Performance Pak – Glock 17, 20, 21, 22, 24, 31, 34 & 35 –  Pak contains 1 each 14 Lb. reduced power recoil spring, 20 Lb. extra power recoil spring, a 5.5 Lb. factory strength striker spring and a 4 Lb. reduced power striker spring. For Generation 1 – 3.  14170