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 should be regularly washed or boiled to remain germ-free and clean. Generally, the filter is not necessary for normal operation; it is intended as an aid for 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 cleaning. This way, the Lucky-Kitty cat fountain requires less frequent cleaning. However, 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 the REACH regulation. The product has been tested for Class I baby products, meaning the parts are free from toxic and hazardous substances even if swallowed.