Recommended Replacement Cycle: For optimal results with your pet water fountain, replace both filter and sponge every 2 4 weeks (more frequently for multiple pets) to maintain a constant supply of purified water Pre Filter fan Sponge: The included thick sponge acts as an additional barrier to collect debris and pet hair before reaching the motor, assisting in maintaining your pet fountain ' s motor durability and supporting uninterrupted water circulation Wide Compatibility: This replacement filter set with fan sponge is designed to fit WF120 12L large stainless steel pet water fountain, providing proper installation and consistent action for your pet water dispenser Advanced 4 Layer Filtration: Contains dense cotton layer, natural shell carbon and resin components to remove particles, hair, impurities and heavy metals from water, offering multi purification for cleaner drinking water Easy Installation Process: Simply soak new in clean water for 5 minutes and rinse thoroughly before use to minimize carbon particles, protecting your pet water dispenser ' s cleanliness and filtration effectiveness