This spring kit will yield a 4.0-4.5 lb. pull with standard AR-15 trigger parts and 3.0-3.5 lb. with JP trigger parts. Application: Use of this spring kit requires the use of US-manufactured (domestic) ammunition or reloads with domestic (non-NATO spec) primers as ignition reliability will be reduced with hard, low-sensitivity primers such as those found in NATO-spec and various foreign-manufactured ammunitions. These springs are for recreational or competition shooting only and should not be installed in any rifle used for defense or duty applications or any AR-10 type rifle. Compatibility: This spring set will function with most any component-style AR fire control system. However, it will not function in our JPFC-M modular trigger.