Just so we're all clear, Helium is lighter than air.
If helium's good enough for balloons, it's good enough for you. That's the theory behind Marmot's Helium 15-Degree Down Sleeping Bag, which, though it isn't actually filled with lighter-than-air gas, still weighs a miraculous two pounds, putting it squarely in the "ultralight" category. You can't make a bag that light and warm by mistake, and it's clear Marmot put some serious work into the Helium―it's filled with super-lofty 850-fill goose down, and the Pertex Microlight fabric is ultralight and treated with a DWR coating to repel water and keep your bag warm through spring, summer, and fall.
The down's high-tech, too, seeing as it's been treated with Down Defender, a water-repellent technology that helps it maintain loft even if some water sneaks through the shell. Cold air won't be able to get near you either, thanks to the Helium's insulated collar, draft tube, and six-baffle Nautilus hood that seals around your face to keep all your hard-earned warmth from escaping into the night. There are stretchy tricot baffles around the head and feet, too, to give you a little extra space without the need for extra material and weight.
- 15-degree lower limit rating, 28-degree comfort rating
- 850-fill down with Down Defender water-resistant treatment
- Mummy bag with sewn-through baffles
- Pertex Microlight nylon ripstop fabric with DWR treatment
- Six-baffle Nautilus drawcord hood with insulated collar and draft tube
- Trapezoidal footbox construction
- Stretch tricot baffles and head and foot
- Stuff and storage sack included
- Filled and finished in the USA