Calibration and conductivity standard solutions... a must in every grower's toolbox. The Bluelab calibration and conductivity standard solutions are essential for use with all Bluelab products for the calibration of pH and testing the cleanliness of the Bluelab Conductivity/Temperature probe. Bluelab solutions are manufactured specifically for Bluelab products and are referenced to high laboratory standards to ensure your Bluelab products last longer and maintain accuracy. Many of Bluelab's conductivity equipment does not need calibrating as they are factory calibrated here at Bluelab. The CF27.7 (2.77 EC) solution is used as a reference or checking solution to ensure you have adequately cleaned the EC/CF probe.