Marmot Hydrogen Sleeping Bag Light Enough to Forget, Warm Enough to Matter When cutting pack weight is the priority, the Hydrogen delivers where it counts. The 800-fill-power goose down is treated with Expe DRY, a water-repellent finish that keeps the insulation lofting and cuts drying time when things get damp out there. Smooth, curved baffles hold the fill in place so warmth stays consistent throughout the bag, and the anatomically designed footbox adds coverage right where cold air tends to sneak in. A secondary fold-down zipper opposite the main gives you a quick way to dump heat when temperatures swing overnight. Features RDS-certified 800-fill-power goose down with Expe DRY treatment water-repellent finish maintains loft and reduces drying time in wet conditions Anatomically designed footbox with wrap-around construction traps warm air and reduces cold spots at the foot end Smooth, curved baffles minimize down migration for consistent warmth distribution throughout the bag Anti-snag slider on main zipper and fold-down second zipper easy entry and exit with added ventilation when temperatures climb | Marmot | Hydrogen Sleeping Bag