Sleek bamboo, toasty wool, or versatile synthetic? When it comes to base layers, there’s a material for every occasion. Use our thin thermal underwear sets all year round and cozy up with our warmest base layers when the mercury drops. Regardless of the season, we have a base layer for you. All our men’s thermal underwear is snug-fitting, moisture-wicking, and fast-drying to keep you comfortable even during the most intense days in the great outdoors.