Compatibility: Only works with Homerunpet fountains; will not work with other brands. Compatible with Homerunpet Wireless Pet Fountain (Model: WF20) What's Inside: Choose from 3-Pack or 6-Pack; Fresh, running water is preferred by your furry friends all day long; so it is highly recommended for families. Triple Filtration: The filter is assembled from coconut shell activated carbon sandwiched between two layers of cotton mesh. It can remove invisible particles from drinking water such as hair, heavy metals and residual chlorine, thus protecting the health of pets' drinking water and reducing the risk of urinary tract infections. How to Use: After unpacking, please soak and rinse the filter for 2 minutes in water. It is recommended to replace the filter component every 30 days, depending on how often your pet drinks and the number of pets accessing the device.