My best friend used to be the sniper on a sheriffs SWAT team, and one day he bought one of those just to throw into his trunk. Snipers often have to lay prettymuch motionless for a long long time, and he figured that in the winter it might help keep him a tad warmer. He tried it out one winter day, just for fun, and said that he sweated like a mule in it, came out soaking wet. Something to consider...