This is a fabulous single-gas computer. Its simple functions will be appreciated by no-nonsense divers, yet it packs several Cadillac features, namely utilizing both numeric and graphic displays for tracking critical dive information. Packaging About half the size of a hockey puck, the Atmos Elite is slimmer than computers of just a few years ago, yet it retains a nice wide screen and easy-to-read numbers. Two buttons operate all modes, including the green backlight. Especially nice is an unobtrusive display guard that snaps securely in place. You'll have no problem wearing this over a dive skin or a bulky drysuit sleeve. Core functions The Atmos Elite operates in three basic modes: air, nitrox and gauge. Gauge mode is good to 395 feet (versus 330 feet for air or nitrox diving). Alarms are both audible and visual, thanks to a flashing LED; however, both can be turned off before the dive. In some cases, though, an alarm will always sound, such as when a diver fails to make a required decompression stop. Centrally displayed throughout the dive is dive time remaining. This takes into account no-decompression limits, oxygen loading and breathing rate. The time displayed is based on the most limiting factor. The Atmos Elite is air-integrated and uses a one-second sampling rate to keep tabs on tank pressure. When calculating air time remaining it accounts for a predetermined reserve amount you entered at the beginning of the dive, so when air time remaining reads "0," there's still time to make an ascent and surface with 500 psi. During ascent, the computer always suggests a three-minute safety stop and provides a countdown; however, if the diver blows through the stop, there is no penalty on the following dive. Finally, the Atmos Elite allows a battery "hot swap," meaning you can change batteries between dives and not lose any of your calculations. Bonus Of course the Atmos Elite features a dive planner, but it also has a simulator. This device allows the user to walk through a typical dive and use all the features and view all the available screens during a multilevel dive.