Calibration Solution PH4 - 8 Oz
A meter is only as good as the calibration. General Hydroponics Standard Reference Solution is available in pH 4.01 (pink) and 7.01 (green). Solution should not be reused. Pour a small quantity from bottle, calibrate meter, and dispose of used solution. Pens should be calibrated about once a week. The storage solution helps prolong the life of the electrode.