Keep Fresh Water The YOUTHINK Automatic Circulating Water Supply Replacement Activated Carbon Filter softens tap water all the time and circulates while removing fur, leftovers, and dust.It has a mechanism to keep water fresh all the time. High-quality product material: Resin: Removes magnesium and calcium in the water, making it gentle on cats (soft water) with a reduced hardness. High Performance Activated Carbon: Absorbs odors and bacteria. Note: Please do not use detergent to clean the filter and clean the surface with water.When replacing the filter, be sure to clean each part of the water supply to keep it clean.