Aero Precision Lower Parts Kit - Includes Takedown/Pivot Spring - Takedown/Pivot Detent - Takedown Pin - Pivot Pin - Bolt Catch - Bolt Catch Spring - Bolt Catch Buffer - Bolt Catch Roll Pin - Safety Selector - Safety Selector Spring - Safety Selector Detent - 4-40 Set Screw - Buffer Retainer - Buffer Retainer Spring - Magazine Catch Body - Magazine Catch Spring - and Magazine Catch Button - Does N