Del-Ton has put together a kit containing all the essential parts you need to keep your AR running. Contains: Four Pivot Pin Detents, Four Pivot Pin Detent Springs, Two Safety Detents, Two Safety Detent Springs, Two Firing Pin Retaining Pins, Two Buffer Detents, Two Buffer Detent Springs, Two Extractor Springs, Two Extractor Spring Inserts, Two Extractor O-Rings.