Ion-X Drinking Fountain Professional Filter for long-lasting fresh water. 4-pack replacement filters, BPA-free, compatible with PetSafe Outlast and Viva drinking fountains. Captures pet hair and coarse impurities, keeping the water clean. The dual filtration system combines activated carbon to eliminate bad taste and odor with an ion exchange filter for soft water without mineral deposits. Precisely fitting and therefore easy to replace. One filter lasts approximately 2-4 weeks, so the 4-pack lasts up to 4 months, ensuring happy and healthy pets.