Kit includes: 1 EZO-DO embedded circuit 1 Dissolved Oxygen Probe 1 Electrically Isolated EZO Carrier Board 3x 20ml Zero Dissolved Oxygen calibration solution pouches 1 Syringe, 1 30ml bottle of Electrolyte Solution The Atlas Scientific Dissolved Oxygen circuit is an electrochemical sensing circuit capable of reading the Dissolved Oxygen of a liquid. This is a commonly measured electrochemical parameter used in fish tanks, swimming pools, hydroponic gardening, pollution monitoring and general chemistry.