The Bluelab Calibration Solutions are a very necessary part of a growers toolbox. These solutions are manufactured specific to the calibration process and referenced to high laboratory standards by Bluelab. They are required for the calibration of pH meters pH monitors and controllers. Regular cleaning and calibrating of pH measuring equipment ensures accurate readings. Bluelab's EC/CF equipment does not need calibrating as they are all factory calibrated at Bluelab. The CF27.7 solution is used as a reference to ensure you have adequately cleaned the EC/CF probe.