Measures windspeed, temperature, altitude, barometric air pressure, and windchill factor. Digital compass shows direction. Keeps a 48 hr history of altitude. Dimension: 3.5 x 1.5 x 0.75 in, 2 oz. (41 x 93 x 17 mm, 50 g) . One button operation. EL Backlight. Completely sealed; internal sensors. Weatherproof (can be submerged 6 feet). Replaceable Lithium battery (included and installed). Stainless steel back. Auto-off after one minute (can be disabled to remain on). Included lanyard. One year warranty. Designed in Switzerland.