This handy device is great for transferring gas from partially full canisters, consolidating fuel into single cans. It is simple to use by placing one can in the freezer and the other in the sun to warm it up then screwing them on to the appropriate inlet/outlet.
I mostly use it to top up a smaller can from ones which are too large to carry with me. This also helps save money as the larger cannisters are often better value and also more readily available.

