Our lower parts kit helps you to build a custom AR15 from the ground up. Mil-spec dimensions and coating ensure the highest quality and correct component interface. This lower parts kit does not include the fire control group, pistol grip or trigger guard. Includes: Takedown/pivot Spring Takedown/pivot detent Takedown pin Pivot pin Bolt Catch Bolt Catch Spring Bolt Catch buffer Bolt catch roll pin Safety Selector Safety Selector spring Safety Selector detent 4-40 Set Screw (for threaded takedown pin detent hole) Buffer retainer Buffer retainer spring Magazine catch body Magazine catch spring Magazine catch button