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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
  • Ultralight
  • 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

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Here's what others have to say...



    This bag is wonderful. I've had a chance now to bring it with me on multiple excursions and it's never let me down. It is down so there's a little extra caution to use when in wet environments but it preforms flawlessly when dry, and I didn't notice any loss of warmth when I rolled over and ended up sleeping against the tent wall with a ton of condensation in the morning. It dried fairly quick too.


    Kept toasty in some extreme conditions

    • Familiarity:I've put it through the wringer

    I have the long version and I'm 6'2. I have room in the bottom for a few pieces of clothing. I've used this bag on an 8 day trek in the Icelandic backcountry highlands. Most nights were at or well below freezing topped off with extreme high winds.
    I slept like a baby and was 100% satisfied the only two things I didn't like was the print on the inside of the bag peeled right off and the stuff sack is a bit small. So I recommend getting a 10L dry bag. I personally couldn't get the bag into the provided stuff sack. I couldn't get it to stay packed down long enough to get it in. It's super lofty. This is the last bag I'll ever buy!


    Fantasticaly Warm Sleeping Bag

    • Familiarity:I've used it several times

    I've only had the chance to use this a couple of outings and so far I have only good things to say about it. It's roomy! My previous mummy bag felt very constricting but this Marmot Helium bag has ample shoulder room. It's fantastic both on the ground (it has enough room and is tight enough that rolling around at night doesn't put your face in the hood...), and it's even better in my hammock. The higher degree fill allows it to be a lighter blanket over my hammock on warm nights, and the extra roominess of the bag really lets it "tuck me in" on cold nights in the trees.

    The only complaint I would have with this bag is it doesn't have the traditional baffles around your neck that I liked to keep out the extra airflow during colder nights, but so far that hasn't been an issue. Happy Camping!


    Stays Lofty 10-Times Longer

    • Familiarity:I've put it through the wringer

    The Marmot Helium weighs just over two pounds, packs down small, has a silky smooth shell fabric, and all of that is great for backpacking, but my favorite thing about this bag is the Down Defender treatment. The treatment makes the down water-resistant, and that means it will maintain its loft for 10-times longer than untreated down. Remember that loft is practically synonymous with warmth, so this is a big deal, especially on multi-day trips.

    Stays Lofty 10-Times Longer

    Too short!

    • Gender:Male
    • Familiarity:I've used it several times

    Very nice bag, but too darned short! I'm 5'9" and the regular size should go to 6'. It's a squeeze for me to get into this bag completely zipped up. I feel like my feet are scrunched in the bottom or head is scrunched in the hood. Marmot must have trimmed some length to loose some weight. Check the length!


    Solid all around bag

    • Familiarity:I've put it through the wringer

    I bought a previous season's model on clearance and have used it on a number of warm and cold weather backpacking trips. The weight and stuff size are great, but for the full retail price you could do better. The stuff sack that came with the bag is a tad small (the bag actually pushes open the draw string), but I've found it fits perfectly in a 10L dry bag.

    With an insulated sleeping pad and a down jacket this bag keeps me warm at 0-10 degrees in late fall in CO, but I don't get too hot on warm summer nights either. I would say the temp rating is accurate/conservative.

    The only complaint I have is that the zipper is cheap and hard to use for a bag in this price range. It doesn't catch on the bag material, but it doesn't zip as well as you'd expect it to.

    Bottom line: If you can get this bag on sale, buy it and it won't disappoint. But for $400, consider shopping around for a lighter/cheaper bag (zpacks, featheredfriends, Enlightened Equipment, etc)

    UPDATE: Just finished hiking the Colorado Trail with this bag and wasn't cold once in the 30 nights I was in my tent. Even camped at 12000' I never needed to wear long underwear or a jacket to sleep. Not sure what temps I saw at night but I think it's safe to say this bag will keep you warm anywhere in CO during the summer. I've had the bag for 2 years and and haven't seen any reduction in loft. This has always been one of my favorite pieces of gear.