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 AR. This kit includes bolt catch spring, buffer retainer spring, disconnector spring, hammer spring, magazine catch spring, pivot detent spring, selector spring, takedown detent spring, trigger spring, bolt catch plunger and roll pin, hammer pin, pivot detent, takedown detent, trigger pin, and a buffer retainer. The Enhanced parts included are a bolt catch, magazine catch, magazine catch button, pivot pin, takedown pin, two SI selector lever, SI selector end plate and a SI 60-90 degree 3-in-1 selector shaft.