I bought several of these for our family's 72-hour bags. We've always had space blankets, which flap in the wind, tear easily, and are hard to wrap securely enough to keep bugs and rain out. These Escape Bivy bags are the perfect answer to sleeping outdoors in an emergency. They're a little thicker and tougher than the Mylar material in space blankets, and they have sealed seams to protect against bugs and rain. They only weigh a few ounces, and the rolled up package is only about the size of a can of soup. These large sized bags are big enough to accommodate medium-to-large sized adults, but probably wouldn't be big enough for really large people. It's important to have it somewhat loose fitting, to trap insulating air in the bag with you. We also like that they come in a draw string bag that's quite a bit larger than the original rolled bivy. I can never roll things up quite as small again, and it's nice to have a bag that accommodates that! We haven't used these in an emergency situation, but I did try one out during a normal night in the woods near our house. The temperature was about 45F after midnight and we had a heavy dew by morning. The bivy bag stayed dry inside, and it reflected enough of my body heat back that I felt warm (wearing jeans, a T-shirt, and socks) and was able to sleep. It would be nice to have a tarp to put down before using the bivy bag because you can feel sticks and rocks through the thin material. But at least the material is strong enough that it didn't get punctured. It was nice to be able to pull the collar of it up around my head and face, which adds to the heat in the bag, and would keep mosquitoes off. Did I sleep deeply in complete comfort? No, but in an emergency situation, this bag will help protect against hypothermia and hundreds of mosquito bites. It's also bright orange, which can help searchers find you if you're lost.