Compatible with many models. Our filters for cat fountains are compatible with various models of 2L, 3.2L, and 4L stainless steel cat fountains. Please be assured to buy our filter, as we are the original manufacturer of high-quality drinking fountain filters. Rest assured, the size is suitable for the specified stainless steel cat drinking fountain models. Package list: The package contains 10 carbon filters and 10 round black foam filters. Three-layer filtration: The cat drinking fountain filter consists of high-quality activated carbon and cotton layers that form a triple filter system, effectively removing hair and heavy metals while improving water taste. Your pet can enjoy clean and fresh water throughout the day, promoting increased water intake and supporting urinary tract health. Regular replacement: The cat water filter should be replaced every 4 weeks. In hot weather, bacteria may multiply more quickly; it is recommended to change the carbon filter every 2 weeks and the foam filter every 2 months to maintain water freshness. Reminder: To minimize activated carbon dust (which is not harmful to pets) from entering the water, soak the replacement filter in water for 5 minutes before first use, then rinse thoroughly under running water.