This cylinder is typically used for nitrogen, helium, argon, and argon / carbon dioxide mixes. This cylinder ships empty but can refilled or exchanged at most gas suppliers. This cylinder ships empty but can refilled or exchanged at most gas suppliers. Please check with your local welding supply to be sure they will fill these D.O.T. approved UN/ISO cylinders. The D.O.T. has approved these cylinders for use in the USA but it is up to the individual supplier as to whether they will fill them.