Did you launch a detent and spring across the garage during your build and now you can't find it? Our Fix-It Kit gets you the most commonly lost parts to finish your build. All parts in the Fix-It kit are compatible with AR15, M4E1 and M5 builds Specifications for Aero Precision AR10/AR15 Ooops Kit: Manufacturer: Aero Precision Color: Black Gun Model: AR-10, AR-15 Condition: New Quantity: 1 Country of Origin: USA Package Contents: Aero Precision AR10/AR15 Ooops Kit Takedown Pin Detent (4) Takedown Pin Spring (4) Bolt Catch Roll Pin (2) Trigger/Hammer Pin (2) Safety Selector Spring (2) Safety Selector Detent (2) Buffer Retainer (2) Buffer Retainer Spring (2) Disconnector Spring (2) 4-40 Set Screw (for threaded takedown pin detent hole) (2) Threaded Roll Pin