Check the listing for details. ISMI Trigger Return Spring for Glock Gen 5 Models 50% Plus Power, Chrome Silicon. Color: Metal, Condition: New. Listed at 7.99 USD. ISMI Glock Gen 5 Trigger Return Spring, 50% Plus Power Designed to fit Glock Gen 5 Models: G17, G19, G19X, G20, G21, G22, G23, G26, G27, G29, G30, G34, G42, G43, G43X, G45, G48. Available at NDZ Performance an increased power trigger return spring for Glock Gen 5 models manufactured by ISMI. These premium springs are manufactured exclusively with Chrome Silicon a certified aerospace specification alloy. ISMI springs are heat treated, shot-peened, and stress relieved after winding to enhance performance and durability. The benefit of Chrome Silicon is that it has a higher yield point of material than OEM springs, which are made from music wire. Chrome silicon springs have 10x the life of traditional music wire springs, and they hold much better tolerances during compression and cycling. The result is a spring that doesn't take as much initial setup as an OEM spring and exerts more load for the entire lifespan of the spring. Upgrade your firearm with ISMI springs from NDZ Performance to improve your firearm's performance and reliability. Note: NDZ always recommends any part be installed by a qualified and trained gunsmith. NDZ promotes the use of safety practices and gear when working on any firearm.