JPS3.5T produces 3.5 to 4 lb. trigger pull with JP Fire Control parts. This kit is intended for use with JP trigger parts and will not necessarily yield substantial change on standard AR-15 trigger components. Application: Use of this spring kit allows for use of ammunition with low-sensitivity primers such as those found in NATO-spec and various foreign-manufactured ammunitions, but in the case of large-frame ARs and duty/defense rifles, domestic-manufactured ammo is strongly recommended to ensure 100% ignition reliability. The JPS4.0 Tactical Spring kit will yield a 4.0-4.5 lb. trigger pull with JP Fire Control parts. This kit is intended for use with JP trigger parts and will not necessarily yield substantial change on standard AR-15 trigger components produces a 4 to 4.5 lb. trigger pull.