You are purchasing one CX900F O-ring. Superior material for your Star-Clear Plus Cartridge Filter Head. This is what you want. Product fits perfectly and is of very high quality. Most sellers will sell the low cost Buna-N or claim a higher grade Viton material, The facts are EPDM is the highest chemical resistance to chlorine and its what you need in your chlorinator. Full List of Compatible Hayward Star-Clear Plus Filters for CX900F Filter Head O-Ring: C1200, C12002, C12002S [C12002(S)], C1502, C17502, C17502S [C17502(S)], C2002, C751, C7512, C900, C9002, C9002S [C9002(S)] Professor Foam product packaging includes 5" x 5" clear plastic zip bag with Professor Foam seal, and Professor Foam manufactured o-ring doubled over in bag. For your pool equipment, trust only Professor Foam brand seals.

• This is the one you have been looking for. Manufactured, tested, packaged & sold by Professor Foam
• Professor Foam seals are high-grade synthetic rubber O-rings to replace old, worn, or cracked o-rings to provide a proper seal for your pool system
• As shown in diagram, this o-ring fits into a groove on the outside of the filter head and seals between the filter head and body
• Compatible with C1200, C12002, C12002S [C12002(S)], C1502, C17502, C17502S [C17502(S)], C2002, C751, C7512, C900, C9002, C9002S [C9002(S)]
• O-Ring image is one o-ring doubled over in bag