The Bluelab� pH Probe Care Kit contains everything you need to clean, hydrate and calibrate pH probes as well as clean and test conductivity (ppm/EC) probes. Probe cleaning and correctly storing pH probes ensures you get the most accurate readings possible and will maximize the life of a probe. Much like the windshield of a car, if it�s dirty you can�t see out! If the probe face is dirty, it cannot read the solution or soil accurately. A tip� if the conductivity reads low, the probe needs cleaning. pH probes specifically, should be kept wet at all times for optimal performance and life.