M&P AR-15 Rifle Customizable Lower Parts Kit -The M&P® AR-15 Rifle Cutomizable Lower Parts Kit is the perfect choice if you want to build a custom AR-15. This kit provides all the parts generally used in an AR-15 build, but allows the flexibility to add popular common after market upgrades Kit Includes; Bolt Catch - Hammer & Trigger PinsMagazine Release Button - Safely Selector Lever Magazine Catch - Takedown Pin - Pivot Pin Buffer Retainer Spring - Magazine Catch Spring Selector Detent Spring - Bolt Catch Roll Pin Buffer Retainer - Selector Detent Pivot Pin Detent Spring - Takedown Pin Detent Spring Pivot & Takedown Detent PinsBolt Catch Spring Bolt Catch Plunger By Smith & Wesson