87% polyester/13% elastane. Dual-layer fabric with an ultra-warm, brushed interior & a smooth, fast-drying exterior. Stretch-mesh back & underarm panels provide strategic ventilation without sacrificing warmth. 4-way stretch construction moves better in every direction. Material wicks sweat & dries really fast. Anti-odor technology prevents the growth of odor-causing microbes. Ergonomic design keeps seams off of high abrasion areas. Mock neck construction for added coverage & warmth.