The O-366 Star Clear II Filter Tank Lid O-Ring by Super Pro is a replacement part specifically designed for Hayward C800F 800/1100 cartridge filters. This o-ring is suitable for use with both the 800 and 1100 models, ensuring a secure and leak-proof seal to keep your pool or spa water clean and clear. Made to the highest standards of quality and durability, this o-ring will help maintain the efficiency and effectiveness of your pool filtration system.