【Compatible】 This replacement filter is only compatible with WF050 WF100 clear fountains. 【4 packs in one set】: You will get 4 pieces of pet fountain filters from one order, which is worth with such quality 【Easy to use】: Thoroughly rinse the filter with water before use, replace it every 2-4 weeks to maintain the freshness of the water. 【Healthy water】: Adopt a high-density, high-density activated carbon filter high content and filter structure is matched with high-density white filter cotton to achieve more filtration, which can effectively maintain water quality, increase oxygen content, and protect pets’ health. Replace every 2-4 weeks, depending on use