Kit includes: zeroed extended bolt catch ar15bolt catch plunger, spring, & roll pin, zeroed trigger guard, screw, & roll pin, trigger & trigger spring, disconnector & disconnector spring, hammer & hammer spring, trigger/hammer retaining pins, zeroed 60/90 adjustable ambi safety, detent, & spring, zeroed ambi magazine catch & spring, zeroed extended magazine release button, hd pivot/takedown pins, detents, & springs, zeroed pistol grip, grip screw, & washer, buffer retainer & spring.Finish your next ar15 lower receiver with the cmmg zeroed mk4/ar15 lower parts kit.Every piece is made here in the usa and comes in convenient color-coded packets to make assembly a breeze.Check out our interactive install walkthrough video below or read the cmmg resources lpk install article for an in-depth breakdown.Dont forget a buttstock or brace kit to complete your pistol or rifle lower.All parts meet or exceed mil-spec.All installation hardware included.