text: The biggest problem with a thermal sight is how you use them and store them. Lesson What makes the thermals so expensive is the front lenses . These are not glass they are made from a mineral called GERMANIUM it is the best heat seeking material there is. However this is a draw back if not used properly. If left out in direct sun it will destroy the lenses and will cost almost a much to repair as to but a new scope. Never look at any heat source with a thermal such as the sun, a welding arc or any heat producing source.