ColdGear Reactor is intelligent insulation that adapts to your activity level for the right breathability & warmth for what you're doing.UA Base 2.0 in sleeves, hood & back is highly versatile mid weight protection for colder conditions & a variety of activity levels.Front panel uses low profile insulation sandwiched between two layers of performance fabric for the ultimate mix of warmth & breathability.Low profile hook & loop at center front allows for ven.