Compatibility: Only works with Homerunpet fountains; will not work with other brands. Compatible with Homerunpet wireless pet fountain ( Model: WF20) What's Inside: Choosing from pack 3 or pack of 6; Fresh and running water is favored by your furry pals all day; thus, it is strongly recommended for families. Triple Filtration: The filter is assembled of activated coconut carbon sandwiched between two layers of cotton mesh. It can remove invisible particles from drinking water such as hair, heavy metals, and residual chlorine, protecting pets' drinking water health and lowering the risk of urinary tract infections. Instructions for Use: After unpacking, please soak and rinse the filter for 2 minutes in water. It is recommended that the filter component be replaced every 30 days, depending on your pet's drinking frequency and the number of pets accessing the appliance.