Kestrel pocket weather meter is the only hand held instrument for measuring wind speed, volume air. flow, win direction, cross wind, head/tail wind, temperature, Delta T, wind chill, heat stress index, relative humidity, dew point, wet bulb, humidity ratio, evapration rate, barometric pressure, absolute pressure, altitude, air density, density altitude & relative air density. Pocket size and seat to use, the kestrel allows you to take fast, accurate reading of the environmental conditions whenever and wherever you are. Kestrel pocket weather meter are made tough in the USA.