Proven in the simplest and most extreme conditions, the Performance series tetratsok is becoming the choice interface for amateur and professional athletes alike. Engineered with AIS technology and constructed with a wicking fiber made of CoolMax? and a resistant outer shell of durable nylon, the Performance tetratsok protects, prevents and out performs any ordinary tube closed sport sock.Anatomical Interface System (AIS) is engineered to separate your toes with a thin, anti-friction membrane that is both lightweight and breathable. Seamless in construction, the tetratsok forms to every contour of your foot. This allows for true restriction free movement from your heel to five toes, encourages healthy circulation, and eliminates skin on skin contact between your toes to prevent blisters from developing.