The Astral Pool auto feeder inline union O-ring is designed for compatible feeder plumbing applications where the union connection needs a reliable seal. An O-ring like this is useful because it helps keep the inline union leak-resistant while preserving the serviceable nature of the connection for future maintenance.This replacement is especially useful when the original O-ring is worn, flattened, brittle, or allowing seepage at the feeder union. Replacing it can quickly improve connection confidence and help restore a cleaner plumbing finish around the feeder assembly.The 4401120102 is a practical service part for compatible Astral Pool auto feeder systems that need renewed inline-union sealing and dependable plumbing support. Astral Pool auto feeder inline union O-ring Designed for compatible feeder union sealing applications Helps restore leak-resistant serviceable plumbing connections Useful when the original O-ring is worn or leaking Supports cleaner and more dependable feeder operation