Pentair U9-362 Union O-Ring Replacement for select Sta-Rite Pool and Spa Filters Union O-ring replacement Fits Sta-Rite System 3 Modular Media pool and spa cartridge filters model S7M120, S7M400, S8M150, S8M500 Also compatible with System 3 SD Series D.E. pool and spa filters model S7D75, S8D110 Fits with Sta-Rite IntelliPro variable speed pool and spa in ground pump This O-ring is designed to use with Sta-Rite FullFloXF Backwash pool and spa valve and also use with Sta-Rite Bronze Pool and Spa Valves