Includes the parts that get misplaced while building your lower including: Bolt catch detent, bolt catch pin 3/32" x 1/2" coiled pin, bolt catch spring, buffer detent, buffer detent spring, disconnect spring, magazine catch spring for AR15, safety selector detent for AR15, safety selector spring, take down pivot pin detent (2 needed/rifle), detent take down spring (2 needed/rifle), hammer spring mil spec, 1/8 x 5/8 coiled roll pin for trigger guard, trigger & hammer pin for AR15 (2 needed) & a trigger spring single stage mil-spec.