PetSafe Drinkwell Replacement Carbon Filter - 16 Total Filters (4 Packs with 4 Filters per Pack) 16 Total Replacement Filters (4 Packs with 4 Filters per Pack) Compatible with PetSafe Drinkwell Avalon, Pagoda and Sedona Pet Fountains Removes bad tastes and odors from the water, keeping it fresh Activated carbon water filter made from organic coconut shells Change every 2-4 weeks to maintain water freshness