PRO2 Oxygen is an unrivalled product which holds more than 3 x more oxygen than can be contained in a similar pressure canister. The ALL NEW PRO2 canisters are filled with 22 litres each of high purity (99.5 %) oxygen.What makes the PRO2 brand special is that it contains an adsorbent which is specially designed to store a much larger volume of oxygen than could be otherwise stored using compression alone. For this reason the device contains and delivers up to three times the quantity of similar container volume products, offering by far and away the best value breathing oxygen on the market. Owing to the new technology, the can may still feel full when all of the oxygen has been used. PRO2 Oxygen contains 22 litres of oxygen in a 750 ml aluminium canister. (Dimensions: diameter 66 mm, height 218 mm).