There are three types of Falcon Gauge Sensitive Altimeters. All of them are housed in a metal case. 1) Three pointer altimeter with barometric window and low altitude warning stripes is a modern type. The easy to read striped sector will show while flying below 16,000 ft. This altimeter type is available in 20,000 ft, 35,000 ft, either inches of mercury or millibars. Over the years, this has proven to be the most popular one. 2) Three pointer Altimeter features a barometric window enable the pilot to adjust the altimeter to the barometric conditions existing at the point of landing . This type is available in 20,000 ft, which can be ordered with window reading inches of mercury or millibars. 3) Two pointer type altimeter features without barometric window. This type is designed to meet the demands of some pilots who either live or fly in an area which has a barometric pressure beyond 1000 millibars. With this Altimeter, the pilot can fly anywhere without worry of barometric pressure changes.