Aero’s 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. Kit includes- 4- Takedown Pin Detents 4- Takedown Pin Springs 2- Bolt Catch Roll Pins 2- Trigger/Hammer Pins 2- Safety Selector Springs 2- Safety Selector Detents 2- Buffer Retainers 2- Buffer Retainer Springs 2- Disconnector Springs 2- 4-40 Set Screws (for threaded takedown pin detent hole) and a threaded Roll Pin. Made in the USA.