AR-15 LPK parts are the individual components found in a lower parts kit for the AR-15 rifle. They include the trigger, hammer, disconnector, safety selector, bolt catch, magazine catch, and the various pins and springs that hold these parts in place. Builders use these parts to complete a stripped lower receiver or replace worn components in an existing build. Each part fits standard mil-spec AR-15 lower receivers and works with upper receivers and magazines.