Duofold Varitherm - Mid-Weight Ankle Length Thermal-Layer Pants spandex,nylon base-layer-underwear closure Soft, seamless fabric stretches four ways for sleek fit and freedom of movement. Better yet, it locks in your body's warmth, for comfort in all conditions. Special fabric technology wicks moisture to keep you dry. Strategic knit-in texture adds breathable ventilation. Tag free and virtually seam free for chafe-resistant softness. Fiber Content: 97% nylon/ 3% spandex