For those cold days when every base layer, mid layer, and shell in your closet just isn't enough..
When we first saw this at APS, everyone was oh-ing and ah-ing. The way it works is pretty cool ..er, make that hot -- that we knew we had to try it.
Just bend the metal disk inside and the liquid crystallizes in seconds, giving off 130 degree heat for quite some time. Keep it wrapped in cloth in a pocket to make the heat last longer.
The best thing is, it's completely reusable. Drop it in a pot of hot water for six to ten minutes until the liquid turns clear again. Once its back to room temperature it's ready to go again!