The Under Armour Women's ColdGear Reactor Vest is a high-performance sleeveless vest that is designed to keep you warm and comfortable during cold weather activities. It is made from a combination of polyester and elastane fabric, which provides excellent stretch and mobility. The vest features ColdGear Reactor insulation, which adapts to your activity level to provide the right amount of warmth. It also has a full zip closure and a stand-up collar for added protection against the elements. With its innovative technology and athletic design, the Under Armour Women's ColdGear Reactor Vest is a top seller on Amazon.