The Strike Industries AR-15 lower Receiver spring replacement kit includes 9 important springs that are commonly replaced or easily lost when building stripped lower receivers. The 9-Piece kit includes springs for the bolt catch, disconnector, buffer retainer, trigger, hammer, magazine catch, selector, and two detents.The Strike Industries AR-15 lower Receiver spring replacement kit includes 9 important springs that are commonly replaced or easily lost when building stripped AR-15 lower receivers. The 9-piece kit includes springs for the bolt catch, disconnector, buffer retainer, trigger, hammer, magazine catch, selector, and two detents. Features: Replace worn springs Commonly used springs Essential for a gunsmith or AR owner