CMC Triggers Complete lower receiver parts kit for AR-15 are 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 Catch2. Bolt Catch Plunger3. Bolt Catch Spring4. Bolt Catch Roll Pin5. Mag Release6. Mag Release Button7. Mag Release Spring8. Buffer Retainer Spring9. Safety10. Buffer Retainer11. Safety Detent Spring12. Safety Detent13. Trigger Guard14. Trigger Guard Roll Pin15. Takedown Detent Springs16. Takedown Detents17. Takedown Pins