Brand New Product! Now you can perform a high and low-RH calibration for your hygrometers.;Simply place your hygrometer inside the bag, close the zipper, and wait 24 hours. A perfectly-calibrated hygrometer will read 32% RH. If your hygrometer reads above or below 32%, adjust the calibration by the number of percentage points it is off from 32%.;Completely maintenance free - no activation required. Easy to use.;Bag Dimensions: 4.5-Inch x 9-Inch.;Lasts approximately one year, good for multiple calibrations. Shelf life before opening the pack is a minimum of 2 years.