The Midweight Men's Thermal Crew Shirt, is the warmest Smartwool base layer available. Constructed from 100% Merino Wool SmartWool Interlock Knit, this thermal shirt is ideal for stop-and-go activities in the coldest weather. Perfect as a stand-alone shirt, or as your primary base layer the 15-603A moves moisture off the skin in its vapor state, guaranteeing dry, warm comfort in cold weather conditions. Features a crew neckline, shoulder panels that eliminate top shoulder seams, and flatlock construction to help eliminate chaffing and maximize comfort. Luxurious SmartWool fiber construction provides maximum breathability and continuous dry performance. Anti-Microbial design eliminates odor. Itch-Free. Washer and drier friendly.