Evolution Electronic Oxygen Conserver. Delivers 5:1 savings ratio at all settings. Minimum 2 year battery life utilizing 2 AA Batteries (average 4 hrs per day usage). Delivers a uniform oxygen pulse from 14-40 breaths per minute. Liter flow increments: 1, 2, 3, 4, 5, 6, 7 Plus CF preset @ 2 LPM. Operating pressure range: 200-3000 PSI. Senses a breath/delivers oxygen in the first half of the inspiratory cycle. Single push button selects the equivalent LPM dosage settings. Weighs only 14.9 ounces with batteries. Auto shut-off feature conserves battery life. Fits easily in virtually any carry bag. 2 year limited warranty. Packaging: 1/Each.