It's known as C3 Anti-Detection Film and comes in two millimeter rolls just like Mylar. One side is composed of Mylar while the other side is a heat resistant material. LEO (Law Enforcment Officials) use a technology called Infared Scanning (IR) for growroom conformations. C3 Anti-Detection Film masks roughly ninety percent of the heat that your garden generates making it almost entirely undetectable to LEO. This material was created in Holland back in the late nineties and since then has been adopted by the United States Military for goverment use which means it is no longer for sale to civilians in the United States. However I did a bit of searching for you and found a place that sells it in England at a very reasonable price. The website address is http://www.greenfinger-hydroponics.co.uk/reflective.htm In addition to it's anti-detection capabilities the Mylar coated side is around 95% reflective if hung properly without bends or creases. I hope I was of help to you regarding this matter. Have a good day.