welcome to our shop! This is a great product that is an altimeter, barometer, thermometer and compass all in one. It is made of high-quality material and is tear-resistant. It is resistant to falling, pressure, cold and heat, and is suitable for various harsh environments. The altimeter barometer has a built-in sensitive air pressure sensor that can measure the real-time air pressure value at the location because the altitude is directly proportional to the location. Atmospheric pressure can be used to measure relative altitude; after the altitude value is correct, real-time altitude can also be measured. The four-in-one barometer, altimeter, thermometer and compass requires no batteries or chargers, no power supply maintenance and repairs, and is sturdy and reliable because it does not require electricity. It is a very good and reliable outdoor tool. A barometric altimeter can predict changes in temperature. Future weather is based on air pressure so you can be prepared for the weather. Progress; easy to carry, reasonable design brings convenience. and the convenience of your outdoor activities. This barometer is equivalent to an altimeter, compass and thermometer. This barometer and altimeter is an environmentally friendly product with a purely mechanical structure. It is specially designed for your outdoor sports such as mountain climbing, mountaineering, and skiing. It is a good partner for your outdoor activities and an essential tool for outdoor sports. 1. Measuring range: (height) 0~5000 meters; (air pressure) 580~1040 hPa; (temperature) -30℃~50℃ 2. Resolution: 20 meters 3. Specifications: length 85×width 68×height 28mm, dial diameter 60mm 4. Measurement accuracy error: height error from 0 to 3000 meters plus or minus 30 meters, error above 3000 meters plus or minus 50 meters, air pressure error plus or minus 5 hPa 5. Storage conditions: temperature between -30℃～65℃; humidity less than 90% Package includes: outdoor compass*1 Contains only the above package contents and does not include other products. Notice: Please allow slight errors due to manual measurement and different monitors. (Customer satisfaction is our top priority, if you find any product problems after receiving the goods, such as damage or incorrect quantity, please contact us immediately. We will try our best to provide you with satisfactory after-sales service) Thanks for getting to know me, I hope this helps. wish you a happy life.