This is a great product that integrates altimeter, barometer, thermometer and compass. It is made of high quality materials, resistant to tears. the fall, at pressure, cold and heat, and is suitable for to various harsh environments. The altimeter barometer tre, with a built-in sensitive air pressure sensor, can measure the real-time air pressure value of the location, because the altitude is proportional to the location. atmospheric pressure, it can be used to measure relative altitude; after the altitude value is correct, the real-time altitude can also be measured. Barometer, altimeter, thermometer and compass are four in one, no battery and charger, no power maintenance and repair, robust and reliable, because it does not need electricity, it is a very good and reliable outdoor tool. The barometer altimeter can predict changes in temperature. future weather based on barometric pressure, so you can prepare for the weather. advance; easy to carry and reasonable design brings convenience. and convenience to your outdoor sports. This barometer is equivalent to have an altimeter, compass and thermometer. This barometer and altimeter is an eco-friendly and environment-friendly product, pure mechanical structure, specially designed for you to do outdoor sports air such as mountaineering, climbing, skiing, etc. It is your good partner for outdoor activities and an essential tool for outdoor sports.