The Bluelab� Conductivity Probe Care Kit is everything you need to clean and test conductivity (ppm/EC) / temperature probes. Proper ppm/EC probe maintenance also ensures you maximize the life of the probe and instrument. The probe surface is where the instrument takes the reading of the solution. If the probe face is dirty or contaminated, the readings may be inaccurate. 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. A tip� if the conductivity reads low, the probe needs cleaning.