ColdGear Reactor is intelligent insulation that adapts to your activity level for the right breathability & warmth for what you're doing. Lightweight, low-profile insulation embedded between two layers of performance fabric for the ultimate mix of warmth & breathability. Internal pocket & audio cord port to hold your phone & headphones. Removable hood with adjustable bungee can be zipped into collar. Tall stand-up collar provides extra warmth & protection. Reflective details deliver greater visibility on low-light runs. Side zipper pockets keep your stuff secure. Extended hem adds extra coverage without added weight or bulk.