Drive DeVilbiss Evolution™ Electronic Oxygen ConserverUOM 1 Per Case For Use With 12 C, D, E or M9 Cylinders Features Delivers a uniform oxygen pulse at increments: 1, 2, 3, 4, 5, 6, 7 Plus CF preset @ 2 LPM Minimum 2 year battery life* utilizing 2 AA batteries Delivers a 5: 1 savings ratio from 14 40 breaths per minute Senses a breath delivers oxygen in the first half of the inspiratory cycle Operating pressure range: 500 3000 PSI Weighs only 14. 9 ounces with batteries Single push button selects the