Springs and detents can easily get misplaced when you are installing them and/or replacing them. Included in this Oops kit are the following items: 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 per rifle), detent take down spring (2 needed per rifle), hammer spring mil spec, 1/8 x 5/8 coiled roll pin trigger guard, trigger and hammer pin for AR15 (2 needed per rifle) and a trigger spring single stage mil-spec. This is must have for your extra / spare kits bin.