The ZEV professional starter spring kit provides a lighter and smoother trigger pull with a positive reset for your Glock 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. *Works for calibers 9mm, 10mm, 380, 40, 45 Auto, 45 GAP and 357. Included Components- CONN-PRO, SPR-TRG, SPR-FPS and SPR-STK-PRO.