This pack with 4 replacement carbon filters is suitable for the PetSafe Avalon and Pagoda ceramic water drinking fountains. PetSafe replacement carbon filters keep your pet's water clean and fresh. Each filter has a duo-density polyester pad that traps hair and dirt, while the carbon removes unpleasant odors and odours from the water, making drinking more attractive. The filters extend the life and should be changed every 2 to 4 weeks, depending on the number of animals using the well.