Product FeaturesCU-A4 3rd Stage: KDF media (or Kinetic Degradation Fluxion Media) with activated carbon. KDF itself is known to kill algae and fungi, control bacteria growth, and remove chlorine, pesticides, organic matter, rust, unpleasant taste and odor, hydrogen sulfide, iron, lead, nickel, chromium, cadmium, calcium, aluminum, mercury, arsenic, and other organic compounds. When used with carbon, KDF can extend carbon filter life for up to 8 times. It also adds a healthy dose of zinc ions to the filter water. Product Highlights Individually wrapped to keep freshness 1/4 in. Quick-Change connections Fits Models RE4T RE5T CU-A4 CU-A3Specifications and Dimensions Length: 10 in., O.D. = 2.5 in. 1/4 in.