High-quality 20 cu ft steel oxygen cylinder with CGA 540 valve. Ships empty! Heavy-duty construction with thick walls and a durable painted finish. The tank has great low-temperature delivery. Guaranteed date of manufacture or hydro test within 12 months. DOT approved. A doctor's prescription is required to fill with medical oxygen. Seek the advice of a physician if you have questions about the proper use of medical oxygen. Please be sure to use a regulator that fits the cylinder valve, and that is correct for your application of use. Product note: compressed gas cylinders can be dangerous if used improperly. Please be careful, know the correct procedures for use, and exercise caution when connecting and using any compressed gas device.