[Compatibility] Perfectly fits 135 fl oz/4L wireless cat water fountain. [Triple Filtration System] Cat water fountain filters feature a 3-layer filtration system. High-density cotton filters hair and debris to keep water clean. Activated carbon removes chlorine and odor, purifying and freshening water. Ion exchange resin filters heavy metals and improves water taste. [Filter Sponge & Pump Sponge] High-density pre-filter sponge further removes impurities for enhanced filtration performance. High-density pump sponge traps particles, preventing them from entering the water pump and helping extend pump life. [Replace Filter Regularly] Replace the filter and sponge every 2 to 4 weeks. Replace more frequently if you have multiple pets. [Warm Tips] Before replacing the filter, soak it for 5 minutes and rinse thoroughly before use. This helps prevent carbon dust from entering the water and keeps the water clean. Product Benefits: Removes impurities Color: As shown in photo Material: Polyester Package Contents: 12 x Replacement Filters 12 x Filter Sponges 12 x Pump Sponges Note: Light reflection and different displays may cause slight color variations between the image and the actual item. Measurement allowance is +/- 1-3 cm.