The M&P AR-15 rifle complete lower parts kit includes everything you need to build your finished lower receiver. All you need is a stripped lower receiver and stock assembly of your choice, and Smith & Wesson provides you with the rest. Includes: Bolt Catch Bolt Catch Plunger Bolt Catch Roll Pin Bolt Catch Spring Buffer Retainer Buffer Retainer Spring Disconnector Disconnector Spring Hammer Hammer Pin Hammer Spring Magazine Catch Magazine Catch Button Magazine Catch Spring Pistol Grip Pistol Grip Lock Washer Pistol Grip Screw Pivot Pin Pivot Pin Detent Pivot Pin Detent Spring Selector Selector Detent Selector Detent Spring Trigger Trigger Guard Trigger Guard Roll Pin Trigger Pin Trigger Spring