The Mares 2mm Ultra-Stretch Flex Socks are made from durable nylon and super stretch neoprene. These rubber socks are great for use with snorkelling or long free-diving fins to protect your feet. They glued and flatlock sewn seams for strength adding durability and ease of donning and doffing. These abrasion. The Mares Ultra-Stretch Flex Socks can also be used under primary boots when diving in extremely cold water for added insulation by layering. The socks have an open cell neoprene foam interior for extreme seal and warmth.