Quick, what's lighter than air, smaller than your pet hamster, and warm enough for summer, spring, and fall camping' If you said the Marmot Hydrogen 30 Degree Down Sleeping Bag, you win! We're out of prizes, but you seem like the type for whom being correct is reward enough. If you feel like getting a prize for yourself, though, the Hydrogen's one hell of a bag weighing an ultralight 1. 75 pounds, it combines Pertex Microlight fabric and 850 fill goose down to make a bag that's rugged and warm, with thoughtful features like stretchy baffles around the feet and head for extra comfort. Down's amazing because it's light, packable, and incredibly warm, but it doesn't work particularly well if it gets wet. To keep the Hydrogen functioning at a high level, Marmot decked it out with a DWR coating, and treated the insulation with Down Defender, which helps down retain its loft even it gets slightly soggy. Dry or damp, you'll be able to cinch down the six baffle Nautilus hood for warmth and seal the face muff around your head while the insulated draft tube keeps cold air where it belongs outside.