Keeps you dry in an emergency, and helps you retain warmth. Completely waterproof so it also has 1001 uses.
AMK says: The most advanced emergency blanket on the market - meticulously designed to never fail when you're counting on it with your life. It all starts with the material, vacuum-metalized polyethylene, that reflects 90% of your body heat while also offering a number of other important features that set it apart from traditional mylar blankets; it opens easily and will not shred if nicked or punctured, rips and tears can be repaired, it is quiet and won't crinkle in high winds, and its high-visibility orange exterior makes it easy for rescuers to find you. Plus, survival tips and techniques are printed directly on the blanket so you have them when you need them. Sized to fit one person.