The Sealskinz Cold Weather Mid Length Hydrostop Socks are 100% waterproof, windproof & breathable mid-length socks. Featuring Hydrostop to reduce water ingress. Perfect for use in colder weather conditions. Sealskinz Cold Weather Mid Length Hydrostop Socks Features Waterproof - three layer construction for warmth, durability and waterproofing Comfort - Merino wool lining for moisture control, insulation and comfort Hydrostop - Reduces water ingress Support - zonal elastication for added support, flat toe seams prevent rubbing Comfort - Footbed padding reduces pressure and absorbs shock Hydrostop Usage Guide - SealSkinz Hydrostop technology creates a seal between the sock cuff and skin, helping to reduce the amount of water from running down the leg and into the sock. Due to this close bond between sock cuff and skin, Sealskinz recommend that Hydrostop socks are only used outdoors and not for a prolonged period of time. Incorrect or prolonged use can result in excessive rubbing against the skin and may in a very small minority of cases cause minor skin irritation. Hydrostop seal material has been fully tested to EN ISO 10993-5: 2009 and is OEKOTEX compliant.