The secret to its intense comfort comes from 100 Grams of siliconized 3M Thinsulate insulation, providing excellent heat retention while letting you move in absolute freedom. Plus the whole vest packs into its own pocket, compressing down to a small package perfect for stowing in a backpack. Down proof nylon shell. Lightweight and highly compactible. 2 external, insulated hand pockets. 1 internal chest pocket.