For what it is worth. The best heater I have ever used. This was made for me (which I am sure you can buy) from a family member. It reminds me of a back support, goes around the waist placing heat at the lower back, it was made out of cloth then I wrap it around latch it with velcro in front, and in the back is three pockets to place the larger hand warmers in. I usaly wear it under my hooded sweat shirt and over some under shirts. When I start getting cold I toss in a couple of warmers and heat right up. I place my hood over my head and you can feel the heat rise right up back and over the neck. It is easy to wear, packs up real small, and works every time. and probley cost $5 to make.
Cb