13 lbs of our exclusive ion-exchange resin for your Portable Water Deionizer. The resin is safe, disposable and easy to install. The life of the resin depends upon the amount of total dissolved solids (TDS) in your water. It is recommended to replace the resin when the TDS of the output water is equal to the TDS of your tap water. Want to know your TDS level? Check out my easy to use TDS meter.