The Growth Technology - pH Probe Refill & Storage Solution 300ml contains: 300 millilitres of Growth Technology pH Probe Refill & Storage Solution How Growth Technology - pH Probe Refill & Storage Solution works: Growth Technology pH probe cleaner is a special storage solution containing dilute potassium chloride. By storing your pH meter probes in the storage solution, the probes will be kept wet and in good condition. Keeping your pH meter probes wet is essential for accurate readings and maintaining the lifespan of your pH probes. Using Growth Technology - pH Probe Refill & Storage Solution: Always shake the bottle well before use. After using your pH meter, clean the ends (preferably using Growth Technologyā€™s pH Probe Cleaner) and then wet the probe in pH Probe Refill and Storage Solution. Depending on the meter, you may be able to pour a little storage solution into the protective probe cap before storing in order to keep the probe wet. Rinse the probe and shake dry before using and discard any used solution. Not recommended for refilling gel-based electrodes.