Generally flasks are meant to be small and discreet, for taking a drink where you normally wouldn’t or shouldn’t. Someone took this idea and blew it out of the water. A one gallon flask is the biggest that I have ever heard of. It can hold five 750 ml bottles! The weight alone would make this thing a pain to carry around.
They call it a hip flask, but I doubt this thing would work very well on a hip, maybe a backpack would better suit it. I know this isn’t really beer related, but it was too impressive to pass up.