The Extech 44550 is a humidity and temperature measuring device in pen form. It has a dual LCD display for simultaneous display of relative humidity and temperature (°C/°F switchable). This temperature pen measures humidity from 20% RH to 90% RH ± 5% RH and temperature from -10°C to 50°C ± 1°C (14°F to 122°F ± 2°F). It has a pocket size for quick and reliable measurements anywhere. The max/min memory function allows the highest and lowest readings to be displayed for both measurements. Includes pocket clip and one LR44 button battery.