Features & Specs Comfortable down to -40°FLayer 1: 2mm of black polyester felt layerWicks moisture away from the footLayer 2: 6mm polyester felt LayerTraps warm airCushions and conforms to the footLayer 3: Metalized polyethyleneDeflects cold airReflect body heat to the footFITS STYLES: ICEBREAKER, FORESTER, WORDAY 2, WORKDAY 3