Extreme temperatures require extreme socks The Horizon Performance Extreme Sock is an over-calf length Primaloft reg / Merino wool sock ideal for freezing conditions whether on expeditions or mountaineering Primaloft s performance fabrics and yarns are primarily designed for next-to-skin comfort to suit a range of activities and combat the harshest conditions The Primaloft reg Silver Merino Wool blend offers an antibacterial finish enhanced warmth superior comfort and unrivalled performance To ensure this sock is as good as it can be we ve added Isolfil polypropylene to wick away moisture keeping the feet dry and hard wearing Cordura in the vulnerable heel and toe areas With elastic grip sections and Lycra the sock retains its shape even after drip drying The result is the very best sub zero expedition and mountaineering sock that money can buy