The Aero Precision standard AR-15 parts kit helps you to build a custom AR-15 from the ground up. Mil-spec dimensions and coating ensure the highest quality and correct component interface.Includes: Takedown/pivot Spring Takedown/pivot detent Trigger/hammer pin Takedown pin Pivot Pin Bolt Catch Bolt Catch Spring Bolt Catch buffer Bolt catch roll pin Safety Selector Safety Selector spring Safety Selector detent Buffer retainer Buffer retainer spring Trigger guard Trigger guard roll pin A2 pistol grip Pistol grip screw Pistol grip lock washer Trigger spring Hammer spring Disconnector spring Magazine catch body Magazine catch spring Magazine catch button Hammer Trigger Disconnector