Inogen One, model G-4 portable oxygen concentrator

Purchased 6/2001, the unit has been used very little as evidenced by the condition. Includes everything that came with the new unit, back pack, day pack, manual, canula, car charger, and 2 batteries. The columns are brand new and have not been used yet. The columns are the part of the machine that actually separates the oxygen from the air. The whole package cost $3295 new. 30 day m 1 y back guaranty if any problems. Fred 303-478-7815