CMC Triggers AR-15 Oops Kit Lower Receiver Replacement Parts Black Small. That's what this kit is for. It's a bag of the small springs and detents that go missing during a lower build stocked deep enough that one kit covers several mishaps. You get the buffer retainer and its spring takedown and pivot pin detents and springs selector detents and springs disconnector springs and bolt catch springs and detent. Keep one on the bench and save yourself a trip Specifications for CMC Triggers AR-15 Oops Kit Lower Receiver Replacement Parts: Manufacturer: CMC Triggers Color: Black Gun Make: AR Platform Gun Model: AR-15 Handle Color: Black Package Contents: CMC Triggers Oops Kit Fits AR-15 Black CMC Triggers CMC-AR15-OOPS: AR-15 Oops Kit Lower Receiver Replacement Parts Black Small