The Zev Technologies(C) Competition Spring Kit contains a heavy trigger spring (heavier is better, as it assists with trigger pull), A reduced power firing pin spring, and a reduced power firing pin safety spring. Installation of the ZEV Technologies competition spring kit provides a lighter and smoother trigger pull for your Glock(R) use in conjunction with the ZEV Technologies pro connector for best performance. NOTE: This item is not compatible with Gen5, G42 or G43 Glock Models. Included Components A ZEV spring kit comes with one of each of the following, a two pound Striker spring, Firing Pin safety spring, & Trigger spring