The Catit Fresh & Clear Cat Drinking Station Replacement Filters 3 Pack are for use with the Catit Fresh & Clear Cat Drinking Station 2L. These filters purifies tap water as well as clearing out any debris such as hairs and dirt in the water. The Catit Fresh & Clear Cat Drinking Station Replacement Filters 3 Pack together with the fountain provide your cat with a fresh stream of clean, filtered water to ensure they stay hydrated at all times.