The Under Armour Men's Coldgear Reactor Exert Jacket is an ultralight, technical insulated designed for working out in cooler temperatures. Its front panel is insulated with Coldgear Reactor insulation optimizes thermal regulation to provide the right breathability and warmth for whatever your activity level. The sleeves, hood, and back are made of Under Armour's UA Base 2. 0 for better warmth where it counts.