Pentair 24900-0503 Drain Plug Replacement for select Sta-Rite Pool and Spa Filters Drain plug replacement Fits Sta-Rite System 3 Modular Media SM series pool and spa cartridge filter model S7M120, S7M400, S8M150, S8M500 Compatible with Sta-Rite System 3 SD series pool and spa D.E. filter model S7D75, S8D110 Fits with Sta-Rite System 3 SS series pool and spa sand filter model S8S70 and S7S50 Also fits with Sta-Rite System 3 Modular SMD Series pool and spa D.E. filters