This national match two-stage trigger from Rock River Arms is an excellent upgrade for your AR15 rifle. It is pre-adjusted from the factory and features a simple drop-in installation. Simply remove your existing hammer and trigger and install your new two-stage trigger in minutes. No adjustments necessary. This kit includes trigger, trigger spring, trigger pin, disconnector, hammer, hammer spring, and hammer pin. The trigger will fit in any mil-spec AR15 lower receiver except Colt (oversize pins).