The Drinkwell Additional Capacity Reservoir (50 oz. size) will keep your fountain filled days longer, doubling the capacity of the Original Drinkwell Pet Fountain. Easy to clean and easy to attach. This product ONLY works with the Original Drinkwell Pet Fountain. Do not put this item in the dish washer. These reservoirs DO NOT work with the Drinkwell Big-Dog Fountain or the Drinkwell Platinum Fountain.