An answer i believe to everybodys cold feet, multipal layers, and perspiration, far-infrared with ceramic reflective fibers, how does it work ? When your are cold, your body expands energy to warm itself. Far-infared ceramic-reflective fibers absorb this energy and reflect it back to you,to much energy and the excess heat will pass through the material and escape, they also wick moisture away from your body, my feet use to get numb standing in 40 degree water, no more ,stood in it for 3 1/2 hrs the other day, no problem, i'll never own any other type of long johns again, oh and don't let the wife get a hold of them you will never get them back,(very soft) e-mail me if interested Doug