These heated socks generated the greatest warmth and were the most comfortable to wear in tests performed by the Hammacher Schlemmer Institute. The socks reached a maximum temperature of 131º F, easily surpassing the 122º F generated by the closest competitor. A rechargeable lithium-ion battery and ultra-thin heating element provide up to 10 hours of warmth on the lowest of four heat settings, compared with 7 1/2 hours of warmth and limited heat control found on lesser models. Unlike inferior socks that slid down and bunched at the ankles, these lightweight socks fit comfortably, leading one panelist to comment "I could barely tell there were wires." According to panelists, the socks "felt silky and were comfortable to wear" thanks to a nylon/Lycra/polyester fabric that also wicks away moisture. The lightweight battery packs can be clipped to a belt or strapped to each leg and require a three-hour charge from the included AC charger. Black/Red. (1 3/4 lbs.)