The Seekins Precision Enhanced Builders Kit contains lower receiver parts as well as the pins and springs needed for assembly of your AR15 lower receiver. Kit includes- Enhanced Bolt Catch Bolt Catch Roll Pin Bolt Catch Spring Bolt Catch Plunger Buffer Retainer Pin Buffer Retainer Spring Mag Release Button Mag Catch Mag Catch Spring Safety Selector Barrel 60/90 Degree Short Safety Selector Lever Long Safety Selector Lever Selector Detent Selector Spring Trigger Guard Trigger Guard Roll Pin Seekins Precision Takedown Pins (2) pivot and rear *Only available in builders kit two Takedown Pin Detent two Takedown Pin Spring Set Screw Hex and two SHCS Hex.