Base layer clothes play a huge role in general comfort as they are in direct contact with your biggest organ - the skin. Synthetic base layers are best for high intensity sports as they are very efficient at transferring moisture, while Merino wool is the prime choice for hiking and backpacking as well as winter use. Merino wool is comfortable even when you stop for a break, and it retains much of its insulation even when moist. As it also requires less washing than synthetic materials, it works just great in back country use. Discover men's merino wool underwear.