Varieties of ORGANIZATION@1 bought and sold include mixes that are primarily propane , mixes that are primarily butane , and the more common , mixes including both propane -LRB- NUMBER@1 % -RRB- and butane -LRB- NUMBER@2 % -RRB- , depending on the season -- in winter more propane , in summer more butane .

Very often , mixes of propane and butane are sold .
