It's a Mobile CPAP Battery Pack. I have a VPAP that I've had since my diagnosis in March, 2009. Have been keeping the bipap hooked up to the battery pack in case of power failure (which occurred Friday night). When the power went out, the battery kicked in automatically. I understand it lasts about 8 hours. I rented the one I used on the plane, but it worked so well that I bought one. Because ALS attacked my respiratory system first, I am now using the bipap most of the time. Having a battery pack that I can use in the car is great! Gary