Superlight And Incredibly Packable. Worn As A Midlayer Or Standalone. The Lightest Atom Vest Offers Summerweight Insulation For Early Morning Runs And Evening Hikes. The Tyono™ 20 Shell Is Light, Breathable, And Wind Resistant, And The Coreloft™ Insulation Is Compressible, Dries Fast And Allows Airflow. Lightweight Stretch Fleece Side Panels Provide Ventilation And Zippered Hand Pockets Stash Small Essentials. All In A Package That Weighs About As Much – And Packs As Small As – An Apple.