I had an interesting talk with the manager of a Gander Mountain Outdoors store. I was killing some time while my wife picked up some gift's. Somehow we got on the subject of emergency camping. You know, your outboard goes dead, your "day long" fly-in pilot never show's up, that kind of thing. I noticed the "three for $6.99" Mylar blankets and asked the man his opinion of them. He stated that they were better than nothing, but not much better. In even fairly mild temperatures, 45 to 55 degrees, hypothermia would be an issue with just a couple Mylar blankets. He also told me the blankets were fragile and wouldn't stand up to abrasion's from twig's, rock's or even sand. Two nights at most and they would be in shreds. He related to me a story about a marathon runner type that was running the North rim of the Grand Canyon and took a "space blanket" with him. He said the blanket was "not enough" at night and that it became useless because of all the rips in it. It was his opinion that the cheapest K-Mart special bag would serve you better. This is from a guy who has made his living testing and selling outdoor equipment from boots to hats to guns.