The Strike Industries AR-15 lower Receiver spring replacement kit includes 9 important spring that are commonly replaced or easily lost when building stripped AR-15 lower receivers. The 9-Piece kit includes spring for the bolt catch, disconnector, buffer retainer, trigger, hammer, magazine catch, selector, and two detents.Package include:- 20 x Bolt Catch Spring- 20 x Buffer Retainer Spring- 20 x Trigger Spring- 20 x Hammer Spring- 20 x Disconnector Spring- 20 x Magazine Catch Spring- 20 x Selector Spring- 40 x Detent Spring Features:- Replace worn springs- Commonly used springs- Essential for a gunsmith or AR owner