The instrument is only as accurate as the probe is clean. Probe cleaning is one of the most important parts of owning or operating any Bluelab meter, monitor or controller. The probe surface is where the instrument takes the reading of the solution or soil/media. If the probe face is dirty or contaminated, then the reading will be inaccurate. Accurate readings simplify crop management and provide improved growth. To re-stock your pH & conductivity probe care kit, Bluelab pH 7.0, pH 4.0 and 2.77 EC Solutions are available in 20ml sachets, 250ml and 500ml bottles. Bluelab pH Probe KCl Storage Solution is available in 100ml bottles only.