Duofold Men's Expedition Weight Two-Layer Thermal Tagless Bottom 100% Spandex base-layer-underwear closure 96% Polyester, 4% Spandex bi-ply fabric. No fly Duofold's Expedition Weight was developed specifically for the U.S. Special Forces for warmth in extremely cold weather 360 stretch for maximum flexibility and optimum fit, excellent moisture management, quick drying and odor resistant TAGLESS for added comfort and flatlock seams to help avoid irritation Imported