The Bluelab Calibration Solution is used for calibrating pH meters, pH monitors and controllers. Regular cleaning and calibrating of pH measuring equipment ensures accurate readings. The Bluelab Calibration Solutions are a very necessary part of a growers toolbox. They are manufactured specific to the calibration process and referenced to high laboratory standards by Bluelab. They are required for the calibration of EC meters, FC meters, pH meters, EC controllers and CF controllers. This BlueLab Calibration Solution - 4.0 pH is used with the BlueLab EC Meter (07010) as well as BlueLab CF27.7 meter (07011).