This lower receiver parts kit for AR-15 is a great addition to your AR15 build. From amateur gun builder to seasoned expert gun smith" this lower parts kit is for you. NOTE: Fire control group and grip NOT included. Kit contains the following: 1.Bolt Catch 2. Bolt Catch Plunger 3. Bolt Catch Spring 4. Bolt Catch Roll Pin 5. Mag Release 6. Mag Release Button 7. Mag Release Spring 8. Buffer Retainer Spring 9. Safety 10. Buffer Retainer 11. Safety Detent Spring 12. Safety Detent 13. Trigger Guard 14. Trigger Guard Roll Pin 15. Takedown Detent Springs 16. Takedown Detents 17. Takedown Pins. All parts meet or exceed MIL SPEC