The Enhanced Lower parts kit offers a convenient upgrade package for the AR15 for those looking for a complete Strike Industries solution for new builds, or to update their plain jane AR. The complete kit features a fire control group which offers a crisp 4.5-5.5 lb pull, with unmatched smoothness for mil-spec style AR15 triggers. This kit includes a bolt catch spring, buffer retainer spring, disconnector spring, hammer spring, magazine catch spring, pivot detent and spring, selector detent and spring, takedown detent and detent spring, trigger detent, pin, and spring, bolt catch plunger and roll pin, and a buffer retainer. It also includes enhanced bolt and magazine catch, magazine catch button, pivot pin, takedown pin, two SI selector lever, SI selector end plate, and a SI 60-90Adeg 3-in-1 selector shaft.