MIDWEIGHT BASE LAYER AND MOISTURE TRANSFER FIBERS - Our 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. An essential feature in all our products, 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+ - 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 7/10 - 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. 4-WAY STRETCH - Fabrics with this elastic feature will hug your body and move with you, eliminating extra bulk, providing a full range of motion, and improving performance. Nearly all our body-fit products include a 4-way stretch. Some of our relaxed fit products include a 4-way stretch as well. Originals II toddler sizes are now available in adorable prints! Constructed with spun polyester yarns for a soft hand feel and spandex giving it a 4-way stretch. The close body fit reduces bulk, and our Moisture Transfer Fibers wick away moisture to keep skin dry and warm. Your toddlers will love the softness of this kids' patterned thermal underwear! *Sold as a set Features: Moisture Transfer Fibers to keep kids dry. Body fit design for next-to-skin performance fit. Easy, comfortable feeling. Crew neckline with self binding. Covered elastic waistband. Fun contrast flat seam. Cuffs for added fit and warmth. UPF 30+ protection. 4-way stretch. Midweight warmth, body fit.