PetSafe Replacement Filter for the Current Dog and Cat Water Fountain, 4 Pack - PAC00-15271 GUARANTEED FIT: The only filter brand guaranteed to fit PetSafe Drinkwell small, medium and large Current Circulating Pet Fountains FRESH WATER: Activated carbon water filter made from coconut shells removes bad tastes and odors from water, keeping it fresh; change every 2-4 weeks to maintain water freshness 50% MORE CARBON: PetSafe Drinkwell branded filters contain 50% more carbon than generic brands for better and longer-lasting filtration PRODUCT SUPPORT: PetSafe brand's US-based Customer Care experts will be glad to help; call Monday through Saturday at 1-800-845-3274 EXPERIENCE: PetSafe brand has been an industry leading US manufacturer of pet behavior, containment and lifestyle products since 1991, helping millions of people and pets each year