2mm Yamamoto Super Stretch Neoprene with our Zirconium liner at the foot reduces water absorption on these form fitting neoprene socks and creates an extra insulating layer. We've increased the length to reduce water entry. Textured bottom helps prevent injury to feet when walking or running on rocky surfaces. They come in handy on long transition runs too.  Available in two sizes, Small and Large.  Size Small recommended for Men's 8 and below, Women's 10 and below.  Size Large recommend for shoe sizes larger than Men's 8 and Women's 10.