1.【Seamless Compatibility】The cat water fountain filter and Pre filter sponge are compatible with 67oz/2L Pet Fountain. 2.【6+12 Pack】Package includes 6-pack of Cat fountain replacement filters and 12-pack replacement filter Sponges. 3.【Premium-grade Filter】The Filter composed of eco-friendly shell→KDF→Ion exchange resin→Coconut activated charcoal→Cotton. It effectively to filter hair, heavy metals, improve the taste of the water and keeps water fresh. 4.【Frequency of Replacement】It is recommended to replace the filter and sponge every 3-4 weeks to maintain water freshness. If multiple cats are using the fountain simultaneously, more frequent replacements may be necessary. 5.【Tips】To prevent coconut activated charcoal dust from shedding into water, please soak the filter in water for 2 minutes and rinse it under running water before using.