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The X-Bionic Women's Energy Accumulator Extra Warm Performance Tights boast more technical features than your average Boeing 747, plus no formal operational training is necessary. Just pull 'em on and they're on auto-pilot--the Energy Accumulator Tights deftly circulate air and warmth while venting excess moisture away. An intricate system of small AirTrap corrugated pads act as air-conditioning channels, while fibers wrap around major muscle groups, drawing heat and moisture away from hotter areas and toward organs that could use a little more warmth. To prevent cold air from escaping when the garment stretches at the joints, X-Bionic incorporated Expansion Ribs in the knee area, which allows the garment to expand without sacrificing performance or warmth.