USED CMMG ZEROED Gunbuilder's Lower Parts Kit AR-15 55CA6BA. Check out our interactive install walkthrough video below or read the CMMG Resources LPK Install article for an in-depth breakdown. All parts meet or exceed mil-spec. Specifications for CMMG AR-15 ZEROED Gunbuilder's Lower Parts Kit: Manufacturer: CMMG Gun Make: AR Platform Gun Model: AR-15 Package Contents: CMMG AR-15 ZEROED Gunbuilder's Lower Parts Kit Bolt Catch Plunger Spring & Roll Pin Trigger/Hammer Retaining Pins ZEROED 60/90 Adjustable Ambi Safety Detent & Spring ZEROED Ambi Magazine Catch & Spring ZEROED Magazine Release Button HD Pivot/Takedown Pins Detents & Springs Buffer Retainer & Spring CMMG 55CA6BA: ZEROED Gunbuilder's Lower Parts Kit AR-15