The Precision Medical Easy Pulse 5 Portable Oxygen Concentrator is one of the best values on the market today.This " MADE IN THE USA " POC is an on demand / pulse delivery system that ranges from 1 to 5 lpm and weighs only 6.8 pounds. This small whisper quiet portable can deliver 6.4 hours of oxygen at a 2 lpm setting with the external battery.This lightweight compact versatile unit is FAA approved for air travel and will operate on overseas voltages.This easy to use unit comes with its own carrying case, A/C adapter for use in any house hold outlet. A D/C adapter to plug into any automobile, boat or motor home. Optional is the external battery that will double the battery life of the unit if used in conjunction with internal battery. An optional back pack carry case is available.