XIKAR hygrometers are manufactured to our exact specifications for long term accuracy and minimal maintenance. They accurately display the relative humidity and temperature in your humidor.Round Hygrometer Features:•1.75" diameter round •This is important because it fits in the same hole as every old analog in nearly every humidor made •Accurate to +/- 2% at 70% humidity •Reads humidity in the range of 20% to 95% •Registers temperature in Fahrenheit and Celsius •One step calibration button. Push and hold for 5 seconds and unit self-calibrate