The Atom Vest is a proven performer across a range of seasons, landscapes and activities. Elevated with advanced insulation and material technologies, this versatile vest delivers its best, most versatile performance ever. Coreloft Compact synthetic insulation retains warmth if wet and withstands years of packing and unpacking, and the breathable, durable Tyono 20 shell resists wind and light weather. Stretch fleece side panels aid ventilation and freedom, and the entire vest packs into its own pocket.