CompatibilityReplacement filter is compatible with WF20/CF20 wireless pumps cat water fountain.Filtration SystemThe filter is assembled of activated coconut carbon sandwiched between two layers of cotton mesh. It can eliminate odors, filter impurities, hair and heavy metals and soften water quality.Water Pump FilterHigh density prefilter sponges further filter debris, prevent clogging and damage to the pump and extend the life of your fountain pump.TipsBefore replacing the filter, please soak and rinse the filter into water for 2 minutes.ReplaceTo maintain the filtering effect, suggest replacing filter and sponge every 30 days. If you have multiple pets, please change the filter and clean the fountain more often.