MIDWEIGHT BASE LAYER - The Hot Chillys Youth Originals ll Ankle Tights are designed for warmth, performance, and wearable comfort; These thermal tights for boys and girls are a long-time kids' favorite with a soft cotton-like hand feel that does not hold moisture; Warm and quick-drying, these kids' base layer bottoms are sure to keep your child cozy and comfortable all season MOISTURE TRANSFER FIBERS - Made with MTF Moisture Transfer Fibers, these children's winter tights move moisture away from the skin to be evaporated so your kids stay warm and dry; The fabric consists of 92% Polyester and 8% Spandex, so the silhouette accommodates movements; The long-lasting construction and heat-trapping technology make these kids' thermal tights perfect for winter outdoor activities BODY FIT - These youth base layer bottoms hug the body for a next-to-skin fit, enhancing breathability and moisture management; Body-fit garments move with your child, eliminating extra bulk and allowing a full range of motion while staying against the skin; This kids' thermal underwear will not get in the way of their daily activities; The close fit reduces bulk and supports use in performance sports as well as causal activities WARMTH FACTOR 7/10 - Ranked from Mild to Hot, the Warmth Factor Thermometer tells you how warm is Hot Chillys thermal clothing; Warmth Factors 6, 7, and 8 are considered Midweight and are very popular for most cold-weather activities; The Originals ll thermal leggings for kids have a warmth factor 7 out of 10; At the same time, these underwear bottoms with UPF 30+ also protect your child from harmful UV rays 4-WAY STRETCH - Nearly all Hot Chillys body-fit thermal underwear for boys and girls includes a 4-way stretch for unlimited movement; Spun polyester yarns with 4-way stretch move easily, eliminating extra bulk and improving performance; The Originals ll kids' thermal pants also feature a gusset and a covered elastic waistband for added comfort