Sta-rite SYSTEM 3 FILTER Union O-rings 35505-1425 2 pack Sta-rite SYSTEM 3 FILTER Union O-rings 35505-1425 2 pack Be sure your ordering current part before you check out, if you not sure e-mail us before checkout Fits DE & Cartridge Models: S7M120, S8M150, S7M400, S8M500, S7D75, S8D110 O-ring size: 4.1" X 0.2" Quality replacement parts by TORK Distributors