This is a home oxygen concentrator, manufactured by Invacare, Model Perfecto2, Model # IRC5PO2V, Serial # 13EF057721. The machine is flawless, and has 5889.95 hours only. It has recently been serviced, (both filters), and is in excellent condition.This model is Home Fill compatible, and can be fitted so it can fill portable cylinders as well if you have a portable unit. The adapter can be purchased from Invacare.The link to the owners manual: /doc_files/1143482.pdfA link to Invacare website where this unit is sold new for $836.00: /cgi-bin/imhqprd/inv_catalog/prod_cat_detail.jsp?prodID=IRC5PO2VI have no use for this unit any longer, and would like to pass along a tremendous savings to someone in need of a perfect unit, this is why I have kept the price so low.$200Please see pictures attached.