This was my mother and father's oxygen concentrator for they died last year
Devillbliss healthcare is the brand
You turn it on and warms up for about 1 minute and then you got oxygen from one to 5 l it works perfect you got to get some tubes I do have some brand new ones and get with you this is a good deal it's usually 5 to 700 dollars new plus shipping so I need to sell it today though