The ZEV professional starter spring kit provides a lighter and smoother trigger pull with a positive reset for your Glock(R) by combining our popular competition spring kit with the all-new ZEV pro connector. The ZEV 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. The ZEV pro connector was engineered to provide users with a consistent, positive reset and a reduction in trigger pull weight without sacrificing the reliability or safety of your pistol. NOTE: This item is not compatible with Gen5, G42 or G43 Glock Models.