The polypropylene yarn maintains the body temperature at the same time as it is breathable and abrasion resistant. This is perfect when you are hiking and your body temperature gets warmer. Along with polypropylene, you have the traceable merino wool that also helps to transport moisture and keep you warm and dry. Terry heel and toe for added protection and comfort. Mesh panels at your top foot for added ventilation, and ribbed panels around your bottom ankle and around your foot for the best support and fit. Socks come in left and right to give you the ultimate fit.