The PetSafe Drinkwell Stainless Multi-Pet Pet Fountain Replacement Filters are designed to fit the PetSafe Drinkwell Stainless Multi-Pet and 360 Pet Fountains. The activated carbon filter removes bad tastes and odours from the water, keeping it fresh. The granulated carbon is made from coconut shells for extended filtration. Replace filter every 2 to 4 weeks. Trust PetSafe to help keep your pet healthy, safe and happy.