Features of the Outdoor Research Men's Tundra Aerogel Bootie Water resistant Wind resistant Insulated Breathable Durable Ankle cinch top Anti-Slip sole Fabric Details 100% Polyester shell, VerticalX 100% Polyester Insulation 200 g/mn++, PrimaLoft Aerogel 1.5mm insert, 60% Polyurethane, 40% Polyester soles