This is the DUI Duotherm 300 Socks Divewear Insulation for Scuba Features: Maximum stretch & low bulk Recommended for 45-60°F great choice for a wide range of water temps! DUI's DuoTherm 300 Socks uses double-layer all-way stretch fleece. Exceptional stretch and warmth. Available in sizes: S, M, L, XL, and XXL. Choice sock for sport and technical divers wanting minimal bulk