Altitech2: Digital Altimeter, Barometer, Compass and Thermometer. Time/Date/Alarms. Chronograph with 24 hour working range. Timer with stop, repeat and up function. Rotating Bezel. Leveling bubble. Carabiner latch. E.L. 3 second backlight. Water resistant. 4" x 2-1/4" x 3/4" 2 oz. Requires 1 CR2032 battery. See more here.