Review on EEEKit 6-Pack Digital Hygrometer Thermometer LCD Monitor - Indoor Outdoor Humidity Meter Gauge for Humidifiers Dehumidifiers, Greenhouse, Basement, Babyroom - Black Round Design, Fahrenheit/Celsius Measurement by Mike Betzing

Good if you are dealing with the metric system. Only worked in degrees Celsius. Revain support thought I was an idiot!? I told them I took the thermometer apart and there was no button to press. I was constantly being told to take a very small screwdriver and "stick it in the hole in the back". All the ones I had didn't have a Fahrenheit knob. However, there was a "hole" at the back.