They're difficult to use for two reasons: 1} The ones being sold where I live have a release--a sliding thumb lever--that you have to slide and hold down to re

They're difficult to use for two reasons: 1} The ones being sold where I live have a release--a sliding thumb lever--that you have to slide and hold down to release fuel...it's part of the neck of the spout...this ties up one hand which would normally be used to either hold the can by the handle, or support it from the bottom...one hand on the handle and one supporting the bottom provide better control when tipping and pouring... 2} The release on the neck is positioned so that there are only a few inches of "free spout" at the end...this makes it awkward to insert it deeply enough into a car fuel tank filler neck... The larger and heavier the can the greater the difficulty...