1. Quality Filter Triple filter system: consisting of a sponge layer and an ion exchange resin layer. Effectively filters hair and heavy metals, keeps the water fresh and improves the taste of the water. 2. Frequency of Replacement To prevent activated carbon dust from entering the water, please soak the cat fountain filter in water for 10 minutes and rinse it thoroughly under running water before use. every 1 to 4 weeks in summer and 2 to 6 weeks in winter. If multiple cats use the fountain, more frequent replacement is required. 3. Easy to for added pet protection. The first filter layer blocks hair and debris, the middle layer removes residual heavy metals, and the third layer ensures healthier, quality flowing water, allowing pets to drink clean, fresh water all day. 4. Compatible with our 108 oz/3.2 L levelwindow cat water fountain. For pet water fountains, the activated carbon filter every 4 weeks and the foam filter every month to maintain fresh water.