Lighter than the original, the Atom SL Hoody is one of the most useful (and packable) pieces you can own. Wear it as a standalone layer when trail runs take you through cold, wet weather or layer it with a waterproof shell when mountain pursuits demand additional warmth and mobility. Breathable and weather-resistant, it has stretch insulation in the body but not the sleeves or hood — maximizing packability while still delivering focused warmth to your core. Need a heavier option? Try the Atom Hoody .