Small parts kit for the AR15 lower receiver. The easiest way to assemble rifles on your receivers. Lower Receiver Parts Kit includes: Buffer Retainer Buffer Retainer Spring Trigger Guard Trigger Guard Pivot Roll Safety Selector Lever, Semi-auto Bolt Catch Spring Bolt Catch Buffer Bolt Catch Bolt Catch Roll Pin Magazine Catch Takedown/pivot Pin Spring Takedown/pivot Pin Detent Magazine Catch Spring Magazine Release Button Pivot Pin Safety Detent Spring Safety Detent Hammer Pin Pin, Rear Takedown