The Men's Shefford Heat Panel Vest delivers lightweight, water-repellent warmth with a shot of exciting technology. The chest and back have interior heat panels powered by a power bank with temperature controlled at the touch of a button. The three temperature settings are: Blue = Low (100°F), White = Medium (113°F) and Red = High (131°F). A power bank with a minimum of 5,000 mAh is required to heat the vest. Power bank sold separately.