Ambient Weather WS-108-WM-2-KIT Portable Altimeter, Barometer, Thermometer, Clock & Compass with Wind Meter This kit combines two of our most popular portable weather meters into one package. The Ambient Weather WM-2 is a comprehensive handheld wind meter with wind speed, temperature, wind chill, wind gust, and Beaufort Scale, all in one compact, portable, rugged package. Other features include wind hold mode, wind average mode, comfort level, low battery indicator, neck lanyard and optional tripod mount. The WS-108 Portable Weather Station includes a digital clock, thermometer, altimeter, compass, and barometer (relative and absolute with sea-level correction), and a weather forecaster. The Keychain Weather Station is big on features and functions, yet small on price and size, and features a convenient carabiner clip for simple carrying and quick access. Includes a powerful backlight for nighttime operation. Perfect for hiking, camping, running, biking, skiing, snowboarding, mountaineering, climbing, boating, kayaking, and outdoor activities, the Keychain Weather Station is a perfect backup to your GPS. Important Note: Altimeters are often misunderstood because they do not measure your actual position on the earth (true altitude) such as a GPS, but measure the air pressure and predict the altitude based on this measurement. This is referred to as Pressure Altitude. Pressure Altitude is adversely affected by the true altitude and to a lesser extent, changes in the weather, often referred to as barometric pressure changes. Thus, your Pressure Altitude can change without changing your position. These changes can be as great as a thousand feet (the changes due to weather are more pronounced at higher altitude). To offset the difference between Pressure Altitude and True Altitude, you must calibrate the device at a known altitude, whenever convenient. WS-108 Dimensions: 2.5 x 2.0 x 0.6 inches, Includes a one year Ambient Weather Factory Warranty.