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Extra wide and extra long, the XXL Mountain Equipment Helium 400 sleeping bag offers big and tall adventurers exceptional comfort and performance on long-distance backpacking trips.

  • Features

    • HELIUM™ 20 outer shell is very light and highly breathable
    • 467g of 90/10 pure duck down has a minimum fill power of 700
    • A wider and longer version of the Alpine fit maximizes thermal efficiency
    • Slanted box-wall baffles throughout reduce weight from the sleeping bag's structure
    • Midlevel side seams afford great versatility whether the bag is laid on its front or back; they also improve even distribution of fill
    • 5-baffle anatomically shaped hood provides high levels of down control, low weight and excellent insulation
    • 4-baffle anatomically shaped and offset footbox restricts down migration while keeping weight and bulk to a minimum
    • Full-length Gemini™ zip baffle and integrated collar with Lode Lock™ closure
    • Comes with a waterproof roll-top stuff sack and storage cube
    • Certified to the Down Codex® standard, which promotes transparency and animal welfare in the down supply chain
    • Mountain Equipment is a member of Fair Wear Foundation, a European initiative working to improve workplace conditions in the garment and textile industry


    Many sleeping bags are rated for temperature by an independent testing protocol. REI and the broader industry now use the International Organization for Standardization (ISO) 23537 protocol, which improves on the older European Norm (EN) 13537 standard; you may still see older items in our assortment that were only EN tested. With either protocol, each bag gets a Comfort (or T-Comfort) rating and Lower Limit (or T-Limit) rating. The Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Ratings are based on a person wearing one long underwear layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38. Many brands use the Comfort rating for women's bags and the Lower Limit rating for men's and unisex bags. Everyone's body and sleep comfort differ, and conditions of use (posture, clothing, sleeping pad R-value, wind, humidity, etc.) affect total insulation, so EN and ISO ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth.
    View all Mountain Equipment Men's Sleeping Bags
  • Technical Specs

    Best Use


    Tested Lower Limit

    27 degrees (F) - EN

    Tested Comfort

    37 degrees (F) - EN

    Temperature Rating (F)

    23 degrees (F)

    Temperature Rating (C)

    -5 degrees (C)


    2 lbs. 4 oz.


    20-denier nylon

    Zipper Location


    Insulation Type



    90/10 700-fill-power duck down

    Fill Weight

    1 pound


    30-denier nylon

    Sleeping Bag Shape


    Fits Up To (in.)

    81 inches

    Shoulder Girth (in.)

    66 inches

    Hip Girth (in.)

    56 inches

    Stuff Sack Size

    11 x 9 x 8 inches

    Stuff Sack Volume

    12 liters

    Compressed Volume




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