Conquer the cold in style with Women's 'HEATTECH'Ultra Warm Crew Neck T-Shirt, UNIQLO's warmest thermal base layer designed for extreme winter conditions. Crafted with advanced 'HEATTECH'Ultra Warm technology, this long-sleeve tee generates and retains heat from body moisture, delivering superior insulation without the bulk. The soft, brushed interior enhances heat retention while offering a cozy feel against the skin. With a classic crew neck silhouette and stretchy fit, it's perfect for layering under outerwear or wearing solo for sleek, thermal comfort. Whether you're commuting, traveling, or enjoying outdoor activities, this thermal top keeps you warm and comfortable all day long.- 'HEATTECH' Ultra Warm Technology: Converts body moisture into heat for maximum thermal insulation.- Extreme Cold Protection: Our warmest thermal base layer, specifically designed for comfort in temperatures ranging from -4°F to 50°F.- Brushed Interior Fabric: Enhances heat retention and provides a soft, cozy feel.- Heat-Retaining Stretch Material: Offers a snug fit that moves with your body.- Moisture-Wicking Performance: Keeps you dry and comfortable in cold weather.- Classic Crew Neck Design: Versatile styling for layering or standalone wear.- Long Sleeves for Full Coverage: Ideal for extreme cold and winter layering.- Ultimate Thermal Base Layer: Perfect for outdoor adventures, travel, or everyday warmth.Compare 3 Types of 'HEATTECH' Fabric:'HEATTECH'- Lightweight yet warm, ideal for everyday layering. - Recommended for 41 °F to 68 °F for mild winter days or cozy indoor wear. 'HEATTECH' Extra Warm- About 1.5× warmer than original 'HEATTECH', offering added insulation without bulk. - Perfect for colder days with recommended temperatures from 23 °F to 59 °F. 'HEATTECH' Ultra Warm - Our warmest option, approximately 2.25× warmer than original 'HEATTECH'. - Designed for more extreme cold with a recommended range of -4 °F to 50 °F.