I don't know about you but I find it very frustrating when I have a one or more part used camping gas canisters with no way of knowing how much is left in them so I always end up taking a spare one "just in case" which all adds the weight to be packed or carried.

Decided when this canister ran out to give myself a point of reference, for this type of canister at any rate. When it ran out I hung onto it and I have just weighed it. Empty it weighs 91g so when I find another part empty one of these by simple subtraction I will know exactly how much gas there is left in it, as long as I remember to check Evernote for this information!