This replacement filter cartridge has technical specifications as Unicel # 7656, Pleatco # PA50, Filbur # FC1240 and OEM # CX500RE. With its 3 inch holes both at top as well as bottom it handles the top load of 50 sq ft. It is 15 5/8 inch long and 7 inch wide and best fit for Hayward StarClear C500, Cal Spas, Hollibaugh Spas, PDC Spas, etc. Provides you clear water for your swimming pools and spas.