PetSafe Drinkwell PAC00-16150 Genuine Premium Fountain Filters Box of 12 - no longer have fountain and have two boxes of 12 available. Filters help extend the life of your fountain and pump and should be replaced every 2 to 4 weeks depending on the number of pets using the fountain. If you have more pets or notice more debris, a slimy feel, or decreased water flow in your fountain, you should clean it more often. Not compatible with the Drinkwell 360 Fountain Model.