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.