Perflex EC50C Aboveground DE Filter System 1.5 HP 25 Square Feet filter internal diameter_4 1 16 inches It is designed for the It is designed for the Sta Rite HRPB High Rate Pool and Spa Sand Filters Models HRPB24 and HRPB30 and Cristal Flo T BP Series High Rate Sand Filter Model T 240BP This is a PVC Tee Fitting with slip (socket) connection that measures 2 1 2 Inch The Perflex Aboveground DE Filters are performance matched with the aboveground PowerFlo Matrix pump to ensure a system that maximizes its filtration ability The Perflex EC50AC's patented Flex Tube design will give you longer cycles between cleaning because the same DE filter powder is used repeatedly