The same working features as the SB-500, the model SB-400 measures altitude to 16,000 feet in 100 foot increments. This model features a mounting plate to allow you to install it in your vehicle. The retaining ring on this unit will accept a lanyard for use away from the vehicle. The hole in each corner of the backplate will accept mounting screws, but using Velcro will allow for less permanent attachment and greater use of the altimeter. The clear and easy-to-read dial can be calibrated to known elevations by simply turning the outside dial. Barometric pressure between 21 inches of mercury and 31 inches is measured on the inner ring.