MIDWEIGHT BASE LAYER AND MOISTURE TRANSFER FIBERS - Base layers are designed for warmth, performance (including but not limited to breathability and moisture management), and wearable comfort; the adventure is yours, we'll keep you warm and comfortable; Hot Chillys exclusive moisture transfer fibers (MTF) move moisture away from your body by employing hydrophobic yarns to wick away perspiration, thereby keeping you dry and comfortable BODY FIT AND UPF 30+ SUN PROTECTION - Designed with 4-way stretch, these fabrics hug your body for a next-to-skin fit, enhancing breathability and moisture management; body fit garments move with you, allowing full range of motion while staying against your skin; ultraviolet protection factor; sunlight includes rays of ultraviolet (UV) radiation, and Hot Chillys products are designed to help protect you WARMTH FACTOR 8/10 - Ranked from Mild to Hot, the Warmth Factor Thermometer tells you how warm each of our products is; warmth Factors 6, 7, and 8 are considered Midweight and are very popular for most cold-weather activities; smooth fabric outside, lightly brushed inside for exceptional warmth in cold conditions COMFORTABLE & WARM BASE LAYER TOP FOR WOMEN - This women's thermal long sleeve is made with a single smooth face and napped back for easy layering and extra warmth without adding bulk; seams set away from shoulder for added comfort; enjoy intimate blend of enhanced polyester and spandex fibers (89% polyester, 11% spandex) BREATHABLE, COOL & FRESH - The women's crewneck top is a midweight base layer with performance materials to combat smell and wick sweat; natural smell control properties remain active for the lifetime of the fabric; activated carbon incorporated into the yarns enhance thermal regulation and smell blocking characteristics of this product