Compatible with Veken automatic flower fountains, and other sizes of the same size. Size: 11.38 cm (length), 1.38 inches (inner diameter).Double action filter: resin and activated carbon. The resin can soften the water and reduce the risk of lithiasis. Activated carbon can absorb impurities and odors, the water stays fresh and clean.The quality of the water can be removed thanks to the three types of filtration. Outer cotton layer on each filter captures hair and debris Three stages of filtration can ensure water quality and improve water taste soft for your cats.Rinse the filter thoroughly with water before use and easily attach it to a fountain.To ensure that the water is clean, the filter should be replaced in time. Replace within 2-4 weeks.