For the warmest overshoe they have ever devised, they had to fundamentally rethink a few key points. For comprehensive wind protection, they rely on GORE-TEX INFINIUM, a fleece-lined material that is also more breathable than any other windproof fabric. Furthermore, an additional layer of Polartec Power Stretch Pro is used. Due to the generally relatively thick construction, only a thinner layer has been used on the inside in the bale area so as not to rub against the crank arm. For maximum warmth, this model is very high and also has solid splash protection. For maximum comfort, we recommend the Venti Soft Sock. Castelli's warmest overshoe for extreme conditions. Windproof and water resistant Gore-Tex Infinium Windstopper material with best possible breathability. Polartec Power Stretch Pro lining for comfortable warmth. Reflective details ensure good visibility. YKK AquaGuard zipper. Extremely durable material on the sole.