Terramar Men's Thermawool Crew T-Shirt, Medium (38"-40"), Light Heather GreyTerramar knows how to engineer natural fibers for a performance base layer. We have been doing it for more than forty years. The thermal men's Crew is designed to keep you warm, dry and comfortable in the mountains, in the woods and any other place you look for challenges. The secret is BLENDING Merino wool with just the right amount of microfibers to make the ideal technical fabric to breathe and manage moisture. We got it right.