Caire oxygen concentrator. Only used at night to sleep. Purchased new cash in 2021. Started letting ins pay and using their concentrator, so this one has been my backup in the guest room. I haven’t needed it, the one they gave me works, so want to sell this one. You can read about it online and check w your healthcare consultants. It is a continuous flow. It is nice to have a backup or a unit you can keep at someone’s house that you visit frequently or sleep over without having to bring it over each time. I bought this one when I had to send the previous one off for a tuneup. Only used at night. 675 cash.