1. compatibility: Our replacement filters are compatible with Lite Pet Drinking Fountain (2.5 liters) and Smart Pet Drinking Fountain (2.5 liters) for 84 fl oz/2.5 L cat drinking fountains. 2. Three layers of effective filtration: Featuring a threelayer filtration design, made of nonwoven fabric, coconut shell activated carbon, and natural ion exchange resin for filtration. It traps hair and dirt, softens water, removes bad taste, heavy metals, and odors, ensuring every drop of water is clean for your pet. 3. Individual packaging: Includes 12 packs of cat fountain filters and 18 filter sponges (6 rectangular sponges, 6 round sponges, 6 columnarshaped sponges). Each filter is individually sealed in clean, hygienic, and moistureproof packaging for added protection. 4. Instructions for use: Before use, soak the cat fountain filter completely in water for 15 minutes, then place it back into the water dispenser. To maintain clean drinking water for your cat, the filter regularly—every 1 to 2 weeks in summer and every 2 to 4 weeks in winter.