INSIDE: 100% Polyester; 70% Polyester/30% Merino Wool Imported Durable Moisture Wicking Fabric: Made of 100% CPT Performance Polyester on the inside and 70/30 Polyester/Merino Wool blend on the outside; Intellifresh freshness protection keeps unpleasant odors from forming on our thermal shirt Regular Fit Thermals for Men: These thermal shirts for men feature a tagless design with flat seams and true sizing for accurate fit Efficient Design: This men's long underwear top has convenient stay-put cuffs and a drop tail that maintains coverage and freedom of motion when worn during various activities Comfortable Base Layer: This thermal underwear is engineered with a dual layering system that traps air between layers, providing a natural barrier of warmth Multipurpose Men's Apparel: Our versatile men's thermal shirt is great for dressing with minimal layers as casual or activewear in very cold to extreme cold weather and medium to high activity levels; Compatible with all-weather sports and activities