L.L. Bean Men's Two-Layer Union Suit, Size Medium Regular, Color Charcoal 50% Cotton / 40% Merino Wool / 10% Nylon Machine wash cold with like colors, tumble dry low. Additional Features: Built with wool so it's warmer than the competition's all-cotton versions. Rib-knit cuffs reinforced with spandex. Nonchafing flatlock seams. One-button, vertical closure in back. Supersoft, nonbinding two-layer construction for warmth and flexibility. Soft, itch-free cotton layer inside for all-day comfort