So instead of purchasing a self heating blanket I'm thinking of saving some money and buying a few foil/silver thermal sheets, like the ones in first aid boxes and putting them inside a blanket and sewing it up, instead of buying a self heating blanket.... Much cheaper and the foil must be the same as that used in the self heating blankets. The theory is the same... It's a silver material that reflects the bunnies heat back at them. Does anyone else use the silver foil sheets?