PetSafe Drinkwell Replacement Pet Water Foundation Filters,Carbon Filter for Dog and Cat Fountains GUARANTEED FIT: The only filter brand guaranteed to fit PetSafe Drinkwell Original, Platinum, Big Dog, Multi-Tier, Outdoor Dog, Mini, Everflow and Zen 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