KE Arms Lower Receiver Parts Kit, 223 Rem/556NATO, Includes A2 Grip (Black), Semi Trigger. Semi Hammer, Semi Disconnector, Semi Selector, Bolt Catch Spring, Detent Spring, Bolt Catch Buffer, Take Down Detent, Bolt Catch, Magazine Catch Spring, Bolt Catch Roll Pin, Magazine Catch Button, Magazine Catch, Front Pivot Pin, Hammer Spring, Trigger Spring, Pistol Grip Screw, Pistol Grip Lock Washer, Selector Spring, Detent Selector, Hammer Pin, Trigger Pin, Take Down Pin, Buffer Retainer Pin, Buffer Retainer Spring, Disconnector Spring, Allen Wrench 1-50-01-543.