The Outus 16 Pieces Sponge Filter is a high-quality sponge filter that is designed to be used in cat water fountains. This filter captures impurities and debris from the water, making it clean and fresh for your pets. It also extends the lifespan of the pump by filtering out impurities. The Outus 16 Pieces Sponge Filter is available in a package that includes enough filters to meet your use and replacement needs.