C.Pig The material is used for insulation in electronic devices like motors, and transformers. It is referred to as DMD for dacron-mylar-dacron. I had a friend who used to sell the stuff, and from time to time, he would give me small sheets that I cut up to the size I needed. Gale Helms (Steve Helms dad)
introduced the stuff to the hobby. He stumbled on it in his work in the aerospace industry. It's likely that there are several manufacturers out there, and that the quality varies a lot. Greg.