The Under Armour Women's ColdGear Reactor Vest is a top-selling activewear vest on Amazon. It is designed to keep you warm and comfortable during cold weather activities. The vest features a sleeveless design and a reflective material that enhances visibility in low-light conditions. It is made from high-quality materials that provide excellent insulation and moisture-wicking properties. The ColdGear Reactor Vest is highly rated for its performance and durability.