wow just looked these up and they are kind of expensive!!
I'm not sure what I'd do with those. I think if someone had an emergency kit of some kind in their vehicle during the winter, they might be nice. However, if I'm in a true survival situation, I'd drinking that thing down without worrying about the warmth as much as it would be nice to have it. They seem too bulky to me to have in any kind of bug out bag.