Active Air 20LB C02 CYLINDER W/ 320 VALVE & BLACKProduct Details Store a large supply of carbon dioxide in a safe, portable container with our 20 pound all aluminum CO2 tank. Sold empty (you must fill with your own supply), the tanks stand 23. 2" high and the slim design won't take up much space in your indoor grow room. Get the best CO2 tanks available. In our tanks, the CO2 cylinder is produced from high strength aluminum alloy. This makes them less heavy than steel tanks and ensures against rust.