The Drinkwell® Replacement Foam Pre-Filters trap any large debris and hair in the water, before they reach the pump, providing cleaner water to your pet. These foam filters help keep the pump cleaner in between cleanings and maintain the fountain's flow rate. These filters are compatible with the Drinkwell® Avalon, Pagoda, Stainless Multi-Pet, 1.8 Litre, 3.7 Litre, and 7.5 Litre Pet Fountains.