Our Waterproof Extreme Cold Weather Mids will keep you dry and warm during frigid stream crossings, on blustery cold and rainy days, through icy terrain and deep snow, and even standing in cold leaky waders. 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.