The only jacket that the Mammoth Unbound Park Staff trusts for over 200+ days on snow, the GT Jacket's durability has been upgraded with our exclusive Thermagraph® Active lining system to keep you going stronger and longer in any elements. A team favorite, the GT's durable GORE-TEX shell keeps the elements out while the Thermagraph Active® lining aids in heat and moisture management as your body heat changes throughout the day.