Same design as Wrightsock's Double Layer Anti-Blister run sock except they substitute insulating ThermaStat in place of Dri-Wright. ThermaStat is a hollow core polyester designed to trap air inside the fiber as an insulator to the outside cold elements. Moisture management is another key element of ThermaStat, coupled with the Wrightsock Double Layer System ensures blister free performance in the coldest temperatures. Flat knit (non cushion) mid-weight sock design. Less bulk doesn't compromise shoe fit. Features a great combination of insulation, moisture management and friction-free control.