Fungivore 749405 Mushroom Bag MyCO2  Mycelium Derived Carbon Dioxide are CO2 bags perfected Unlike all the other CO2 bags that 'come cultivating CO2 even before you get out of the checkout line,' MyCO2 has the patent pendingcustomer activation technology, postponing the CO2 cultivation until you get it home and are ready to use it One CO2 bag provides enough carbon dioxide for flowering or vegging plants in a 4 ft x 4 ft grow tent with cycled exhaust