Zoo Med's Precision Analog Gauges are of professional breeder quality, with many features not found in cheap imported gauges. Features include European-made precision German movement, side-venting to prevent against "fogging" inside the thermometer, and Velcro backing enabling you to remove the gauge for terrarium cleaning and maintenance. Accurately reads the amount of water vapor saturation (humidity) in the air of your terrarium. Range is from 0% to 100%.