A strong ally for those who feel the cold, Uniqlo's "Heattech Extra Warm (Kiwami-Dami)" is a high-performance innerwear that provides approximately 1.5 times the warmth of regular Heattech. It's perfect for cold days and situations where you spend a long time outdoors, as it increases the bulk of the fibers to trap more air, and the back side has a micro-fleece finish to retain air. Heattech's unique material has a moisture-absorbing and heat-generating function that converts water vapor from the body into thermal energy, and the air layer created between the fibers traps warmth, providing a warming effect. The Extra Warm type also incorporates argan oil into the fibers, creating a smooth texture that gently envelops dry winter skin. The elasticity has also improved by approximately 20% compared to the previous version for women, offering a comfortable fit that minimizes tightness. In addition, it has seven Heattech functions (heat generation, heat retention, moisturizing, quick-drying, antibacterial and odor-resistant, stretch, anti-static, and shape retention), quickly absorbing and wicking away sweat while providing warmth and a dry feel. It also has a moisturizing effect thanks to the milk protein blend, and the antibacterial and odor-resistant treatment suppresses unpleasant odors. Furthermore, the special knit fabric prevents shape loss and wrinkles from washing, maintaining a beautiful silhouette. The XL size and off-white color are less likely to show through outerwear, and while thin, they are warm, making them useful as innerwear for everyday wear and loungewear.