They changed the product on me..an oxygen concentrator.. the original machine had all the features I was looking for..a 1l to 6l changeable oxygen levels with nebulizer.. they said the one I paid for was no longer available but the had an equivalent oxygen concentrator with nebulizer.. that was a lie.. and on the same day I received the machine and it didn't work.. no oxygen and nebulizer doesn't work. They refused to give me back my money. Got this letter.. **Read the owner manual. Warning: The first concentration of this product is 35%, it is a health-care type, non-medical grade, medical grade advice is required to buy a professional machine, please strictly follow the product manual, or find a professional to guide the use, to avoid misunderstandings due to improper operation , Products undergo strict quality inspection before leaving the factory. ***There was no manual.. the machine I paid for .. Home use portable oxygen generator O2 Concentrator Air purifier machine with Anion and nebulizer function 110V (1-6l/min) I am a retired Nurse. So I know how to work the Machine.. and it's a scam .. they say it's a 30 day money refund on return policy .. they refuse to honor their refund policy.