COLOR-CHANGING DEIONIZATION RESIN – AquaticLife Mixed-Bed Deionization Filter Cartridge contains positive Cations and negative Anions, each in a different color. DI Resin physically changes colors from Blue to Tan when the media is exhausted. REDUCES TOTAL DISSOLVED SOLIDS TO ZERO – The deionization resin is necessary to reduce Total Dissolved Solids (TDS) to zero in the final stage of an RO/DI system. It uses ion exchange to remove TDS from water. 10-INCH STANDARD SIZE FILTER – 10-inch mixed-bed DI filter cartridges fit popular RO/DI systems and the Aquatic Life Spot Free Car Rinse. The opaque housing allows for easy detection to know when it’s time to replace the resin. THREE REFILLABLE CARTRIDGES – Cartridge caps unscrew to allow for refilling with AquaticLife bulk resin. Compatible with Captive Purity, Kent Marine, Seachem, Coralife, BRS, and most other residential or aquarium/hydro DI and RODI systems. UNSURPASSED QUALITY AND SATISFACTION – AquaticLife manufactures an assortment of water filtration equipment. Every product that goes out the door meets our highest standards and quality.