Compatible Fountain: This spare Cat fountain filter is only compatible with the Petrolo 71ZO/2.1L PLWF002 fountain. Please check your fountain model before purchasing p> Keep pure water all day: It is composed of a layer of cotton, activated carbon and ion exchange resin. The pet water filter can effectively capture hair and heavy metals, maintain the freshness of water, and always improve the taste of water p> Keep your pet healthy: The liquid fountain with this filter can help your pet increase water use and reduce the risk of urinary tract infection P> 8 high-quality filters with 8 sponges: You will receive 8 bags of separately packaged and sealed high-quality pet fountain spare filters, as well as 8 sponges Tips: Before use, the filter must be thoroughly washed under running water, and then soaked for 3-5 minutes to obtain better results. We recommend changing the cat or dog filter every 2 to 4 weeks