Sooo...... i called Roberts Oxygen and asked how much for a 20lb co2 tank exchange and it was 28$. the 5lb exchange at the same one is around 25. i couldnt believe that the 20lb was almost the same price as the 5lb one. glad i have the 20lb one now. going to use the 20lb one to carb the beers and the 5lb ones to just push the beer out of the kegs.