This permanent filter extends cleaning intervals and filters out small particles like crumbs from cat litter or food residues, keeping them away from the pump. Additionally, it provides extra support for the pump. The filter is a sponge-like permanent filter, meaning it lasts for many months and can and should be regularly rinsed or boiled to keep it germ-free and clean. Generally, the filter is not necessary for normal operation; it is intended to assist with long-haired cats or for cat owners with multiple cats using the Lucky-Kitty, or for those whose cats tend to bring litter or food scraps into the drinking fountain. Of course, it can also be effectively used with short-haired cats if you want to save on some cleaning. This means the Lucky-Kitty cat fountain will need to be cleaned less frequently. We still recommend at least one thorough cleaning per week, for the sake of the cats. The material meets the high ÖKO-TEX Standard 100 and is free from harmful substances according to REACH regulations. The product has been tested for Class I baby products, meaning the parts are free from toxic and hazardous substances even if swallowed.