Aero's 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. Kit includes- Takedown/pivot Spring, Takedown/pivot detent, Takedown pin, Pivot pin, Bolt Catch, Bolt Catch Spring, Bolt Catch Buffer, Bolt Catch Roll pin, 4-40 Set Screw (for threaded takedown pin detent hole), Safety Selector, Safety Selector Spring, Safety Selector Detent, Buffer Retainer, Buffer Retainer Spring, Magazine Catch Body, Magazine Catch Spring and Magazine Catch Button.*Note- This lower parts kit does not include the fire control group, pistol grip or trigger guard.