The M&P AR-15 Rifle Customizable Lower Parts Kit is the perfect choice if you want to build a custom AR-15. This kit provides all the minor parts generally used in an AR-15 build, but allows the flexibility to add popular common aftermarket upgrades. Kit Includes: Bolt Catch Bolt Catch Plunger Bolt Catch Roll Pin Bolt Catch Spring Buffer Retainer Buffer Retainer Spring Hammer Pin Magazine Catch Magazine Catch Button Magazine Catch Spring Pivot Pin Pivot Pin Detent Pivot Pin Detent Spring Selector Selector Detent Selector Detent Spring Takedown Pin Takedown Pin Detent Takedown Pin Detent Spring Trigger Pin