Omni-Wool Mens Dual Base Layer Long Sleeve Crew Neck Shirt Outer Layer Material: 80% Polyester, 20% Merino Wool, Inner Layer Material: 100% Polyester Merino Wool blend base layer thermal top is endurance tested to keep you warm, dry and comfortable Dual-layer system: Outer Layer absorbs moisture and transfers to air. Inner Layer moves moisture from skin to outer layer and dries quickly. Soft, breathable, dual-layer fabrics that stretch for optimum fit and product design allows for maximum freedom of movement Flatlock stitch construction for superior seam strength and flat seams for comfort Machine wash, tumble dry, do not iron