[Compatibility]perfectly for 135 fl oz/4L wilreless cat water fountain. [ Triple Filtration System]Cat water fountain filters come with 3 layer filtration system, high density cotton can fliter hairs and debris, keep water clean; Activated carbon can remove chlorine and odor, purify and freshen water; Ion exchange resin can filter heavy metals and improve the taste. [Filter Sponge& Pump Sponge]High density pre-filter sponge can further filter out impurities, fully the filtering effect; High density pump sponge can filter impurities, preventing them from entering into water pump, it can help extend pump life. [Replace Filter Regularly]Suggest replacing the filter and sponge every 2 to 4 weeks; Please change them more often if have multiple pets. [Warm Tips]Before replacing the filter, please soak the filter for 5 minutes and thoroughly rinse it before use, which will prevent carbon dust from shedding into water, keep water clean. Product Benefits: Removes impurities Colour: Material:Polyester Specification:12Set Package Contents: 12 x Replacement Filters 12 x Filter Sponges 12 x Pump Sponges