Note:Due to different production batches, there are slight differences between the actual product and the picture, which will not affect normal use. Calibration Solution for pH meters, is a solution of a known and fixed pH level that is used to calibrate pH meters. It can also be used to check the accuracy of pH meters. The pH buffer should be used regularly to ensure that the pH meter readings are accurate, as an incorrect acidity level of the nutrient solution can result in your plants not being able to take in the nutrients they need. The pH meter requires at least a two-point calibration. For example, if you need to calibrate the pH reading on the meter, both a pH 7 buffer and a pH 4 buffer are required. How to Calibrate the pH Meter: 1. Rinse the electrode with clean water and wipe it dry. Turn on the pH meter and adjust to pH mode. 2. lmmerse the electrode in the pH 7.00 buffer solution and wait for the reading to stabilize. Press and hold the "CAL"button for 5 seconds the screen will display "CAL" and the pH 7.00 calibration is complete when pH 7.00 flashes 3 times. 3. Rinse the electrode with clean water and wipe dry. 4. Repeat the above calibration steps to calibrate pH 4.00 and pH 10.01. Notes: 1. Keep the electrode moist to ensure the life of the electrode. If it is dry, only three drops of protective liquid are needed. 2. After using the calibration liquid, wash the probe with clean water to avoid contamination of the calibration liquid by residual liquid carried by the probe. 3. After using the calibration liquid, please tighten the cap to protect the liquid, which can be reissued for use. 4. For you to protect the liquid, please store the liquid in a cool place where the sun does not shine directly. 5. It should be put in a place where children can not take, to avoid accidental ingestion. Colour:As Shown Material:Plastic Package Contents: 1 x 50ML 4.00 PH