ECWS Intermediate Sleeping BagThe ECWS (Extreme Cold Weather System) is a modular sleep system from the U. S. Military. The system is made up of 3 items the intermediate sleeping bag, patrol bag, and bivy bag. When all 3 bags are used together they are rated for use at 40 degrees Celsius. This is just the Intermediate sleeping bag which can be used on its own, rated at 23 degrees Celsius. It is worth noting that these ratings are based on what temperature you could survive in for