The Blue lab Probe Care Kit contains everything you need to clean and test conductivity (ppm) probes.
A tip: If the conductivity reads low, the probe needs cleaning. The probe surface is where the instrument takes the reading of the solution. If the probe face is dirty or contaminated, then the reading will 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 accurately. Proper probe maintenance also ensures you maximize the life of the probe and instrument.