- Updated to Ultra Stretch fabric with added deodorizing features for comfort. - Lightweight while maintaining the same warmth. - 'HEATTECH' Ultra Warm is approximately 2.25 times* warmer than regular 'HEATTECH', with a brushed interior for an extra soft feel. *Based on CLO values, which indicate the thermal insulation of clothing. Compared to regular 'HEATTECH'. - Fabric with HEAT RETENTION, Heat of Absorption, moisture-wicking, ultra-stretch, and deodorizing comfort features. - Body width and full-length sleeves designed for the feel of a long-sleeved T-shirt or sweatshirt.