TempPro TX-2C: Additional sensor for TP65C and TP200C (If the product you purchased is an old model that has been discontinued such as TP65, TP65S, TP60S, etc., the transmitter that these models are compatible with is B0711T22R6) The outside sensor comes with and powered by 2 x AAA 1.5V batteries Temperature range: -20 to70 degree Celsius; Temperature tolerance: 2.0 degree Fahrenheit or 1.1 degree Celsius Humidity range: 10 to 99 percentage relative humidity; Humidity tolerance: 2 percentage relative humidity from 30 to 80 percentage relative humidity; 3percentage relative humidity below 30 percentage relative humidityand above 80 percentage relative humidity ThermoPro is now TempPro! TempPro will maintain same mission, same operation backbone and same products as ThermoPro; You may receive either a ThermoPro or TempPro branded product