No one has to know that your obliviousness to the cold is battery powered. But you should know how it works in the event your secret is exposed by an envious hunting buddy. Rest assured it's not alien derived technology. Simple laws of conductivity come into play with our patented Thermo-Tex. Yes, ink. It's not your garden-variety ballpoint ink. It's special silver-based ink that carries a warm current throughout the garment. The heated traces of ink throughout the garments are coated in polyurethane so you can't wash, sweat or rub it off. It's pretty cool. And warm.