20 oz Aluminum CO2 Tank The MOST popular size of CO2 tank. This lightweight aluminum CO2 tank is BRAND NEW from the factory for years of trouble free use. The brand of tank may vary but will be from a major supplier of CO2 tanks; Typically Pure Energy/Extreme Rage (PMI) or Guerrilla Air. A 20oz tank may deliver anywhere from 800-1200 shots per fill. Actual performance may vary based on gun type, set-up, and individual playing style. Please note: By law, we are required to ship all CO2 and HPA tanks empty. Tanks will need to be filled prior to use.