ZEV Technologies Professional Starter Glock Spring Kit. 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. Specifications for ZEV Technologies Professional Starter Spring Kit: Manufacturer: ZEV Technologies Color: Multi Gun Make: Glock Gun Model: All Glock Gen 1-4 except Glock 42 Glock 44 Condition: New Package Contents: ZEV Technologies Professional Starter Spring Kit What firearm models does the manufacturer say ZEV Technologies Professional Starter Spring Kit is compatible with? The manufacturer suggests that ZEV Technologies Professional Starter Spring Kit is compatible with All Glock Gen 1-4 except Glock 42 Glock 44ZEV Technologies SPR-START-KIT-PRO: Professional Starter Glock Spring Kit