Drinkwell® Replacement Charcoal Filters keep your pet's water tasting clean and fresh. Each filter features a duo-density polyester pad that catches hair and debris, while the charcoal removes bad tastes and odours from the water making it more appealing to drink. Filters help extend the life of your fountain and pump and should be replaced every 2 to 4 weeks for maximum freshness. Keeps your pet's water clean by removing bad tastes and odours from the water PetSafe Drinkewell filters contain 50% more carbon than generic brands for better and longer-lasting filtration Easy to replace, each filter provides 2-4 weeks of filtration Compatible with these Drinkwell Fountains: Original, Mini, Zen, Multi-Tier, Everflow, Outdoor Dog, Big Dog, Platinum Available Size: 3-Pack