Customization is endless with the AR15 platform, which is why the CMMG ZEROED Mk4/AR15 Gunbuilder's Kit includes all of the essential parts except the most commonly upgraded ones: Trigger Guard, Fire Control Group, and Pistol Grip. 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. All installation hardware included.Kit Includes:Bolt Catch Plunger, Spring, & Roll PinTrigger/Hammer Retaining PinsZEROED 60Adeg/90Adeg Adjustable Ambi Safety, Detent, & SpringZEROED Ambi Magazine Catch & SpringZEROED Magazine Release ButtonHD Pivot/Takedown Pins, Detents, & SpringsBuffer Retainer & Spring