The Bluelab Calibration 250ml Solutions are a very necessary part of a growers toolbox. They are required for the calibration and checking of Bluelab meters and controllers. Our solutions are manufactured specific to the calibration process and referenced to high class laboratory standards by Bluelab. Bluelab's EC/CF equipment does not need calibrating as they are all factory calibrated here at Bluelab. The CF27.7 (EC2.77) solution is used as a reference or checking solution to ensure you have adequately cleaned the EC/CF probe. Calibration Solutions should be stored in a cool place out of direct sun and heat. Please keep out of reach of children. They should be stored with the lids securely tightened. Not replacing the lid after use will result in evaporation which causes the salt content in the solution to rise decreasing the validity of the solution. Contamination between solutions can easily occur, which will affect the validity of the calibration. Bluelab recommend that the solutions are de-cantered into a smaller vessel and the contents discarded when the calibration process has been completed.