I bought the thermometer to measure the internal temperature in my terrarium can. The hygrometer I need also. Fastenings, with an adhesive strip on the glass roof, it measures about 15 cm in height, the temperature. And my two turtles can not reach it and chew .... Whether it measures exactly, I've checked. The temperature of the internal sensor (in the device housing) agrees to within one degree difference with the temperature of my digital alarm clock match. That's enough for me.