Scope of application: Replacement filters for PETLIBRO 71oz/2.1L Water Fountain PLWF002. Please confirm size before . Quadruple filtration for pure, fresh water: doublelayer polycotton filters out hair, sediment and debris; activated carbon absorbs impurities and odour; natural resin removes residual chlorine, odour and softens tap water; mafic stone adsorbs surface bacteria to improve water quality. Safer materials and construction: each component is tightly sealed inside with a strong layer of quality PP cotton, preventing leakage and ensuring no obvious carbon particles in the water. Natural larger particles of coconut shell activated carbon and ion exchange resin are filled more fully than older versions, delivering stronger purification and longer use time. Health benefits: filters impurities in water, reduces dust and odour from the air, softens water, removes heavy metal ions, and provides fresh, healthy water for your pet. Use and maintenance: before first use, soak the filter in clean water for about five minutes to fully wet it and maximize effectiveness, reducing production dust contact. every 12 weeks in summer and 24 weeks in winter, depending on usage and water quality. Replacement indicator: if the fountain light turns yellow, the filter should be replaced. Compatibility note: compatible with PETLIBRO 71oz/2.1L PLWF002 fountains; please confirm size before .