Humidipak® Patented One-Step Hygrometer Calibration Kit is used to check the accuracy of your hygrometer. The One-Step Calibration Kit produces an environment of 75% humidity. To calibrate, place your HygroSet™ Digital Hygrometer into the ziplock bag (included). If adjustment is necessary, your HygroSet™ features an adjustment knob to zero in on the correct humidity reading. The HygroSet™ is the first digital hygrometer in the cigar industry to have this feature.