It's 3M new Sherry efficient velvet. Sherry velvet is a registered material trademark of 3M Company, and it is one of the famous brands of thermal insulation materials. Its design concept is light weight and warmth. It was originally designed and developed for the warm clothing of the US Marine Corps. The reason why sherry keeps warm is mainly by the air retained in its fiber. The more air retained in the fiber, the less heat loss will be conducted, and the higher the thermal efficiency of the material will be.