LiquaGen Portable Aquarium-Countertop Reverse Osmosis Water Filter System-DI/RO : 4 Stage System Membrane This is an installation - free Reverse Osmosis Water System which is great for aquariums, laboratory testing, and other applications where ultra-pure water is necessary. Filtration Stages : 1st Stage : Inline Sediment Filter, 2nd Stage : Inline Carbon Filter, 3rd Stage : Reverse Osmosis Membrane, 4th Stage : Inline DI Resin Cartridge Faucet Adapter is included with all necessary tubing & connections.