Merino wool and a highly elastic, highly insulating synthetic blend provide the most insulation of any of our skin layers, with an updated neck-warmer collar construction that extends the protection. The ultrasoft textile doesn’t irritate like wool, and its high elasticity means it also doesn’t lose its shape when it stretches. Instead, it moves with your body, maintaining a low-volume, next-to-skin fit to trap warmth and expel moisture – both of which are critical for comfort in deep winter.