The SealSkinz Stanfield Waterproof Extreme Cold Weather Mid Length Sock is a 100% waterproof, windproof & breathable mid length sock. The inner lining is crafted from fine Merino Wool to insulate and regulate temperature making this perfect for use in very cold conditions. SealSkinz Stanfield Waterproof Extreme Cold Weather Mid Length Sock HighlightsWIDE RANGE OF ACTIVITIES Waterproof and warm, they're an ideal choice when you're at risk of getting wet in snow, ice, mud or rain while out hiking, fishing, cycling, or running in extreme conditions.BUILT FOR EXTREME TEMPS Crafted with the thickest insulation, this sock is ideal for extremely cold and wet conditions where thermal retention is imperative. Using a three-layer bonded construction, a 100% waterproof hydrophilic membrane is sandwiched between a premium Merino wool interior for warmth and a durable nylon exterior with 4-way stretch lending to great fit and wearability.AN ADDED LAYER OF WARMTH Designed with warmth in mind these socks are constructed with the finest Merino wool and an added a layer of terry-loop knitting. This loop knitting actually traps heat within the air pockets keeping you warmer when you're in the coldest conditions.