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  • Marmot - CWM Sleeping Bag: -40 Degree Down - Team Red/Redstone
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  • Marmot - CWM Sleeping Bag: -40 Degree Down - Team Red/Redstone

Marmot CWM Sleeping Bag: -40 Degree Down

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    • Team Red/Redstone

    11 Reviews


    Engineered for the world's harshest environments.

    Get some shut-eye in the death zone with a little help from the Marmot CWM -40 Degree Down Sleeping Bag. This 800-fill goose-down-insulated bag is built for the coldest, harshest weather on the planet, from the South Col to the South Pole. Its waterproof, breathable Pertex Shield 2L laminate prevents rogue bits of water, tent condensation, and melted snow from clumping your down and ruining your sleep (and chances of summiting tomorrow). The outer fabric itself is made from rugged 30D nylon ripstop and the lining from 30D nylon ripstop Pertex Microlight, which has a soft feel and the durability to prevent feather leaks.

    Cross-baffle construction keeps down from migrating and the wrap-around footbox traps heat ultra efficiently and lets your feet sit comfortably. The CWM comes with a drawcord hood with easy-grab cords, a warm down-filled neck baffle, and zipper draft tube to seal up all the gaps against the unrelenting cold and make sure all your body heat stays close, where it belongs. The draft tube also sports a hidden pocket so you can access small gear without having to unzip in the middle of the night, and Marmot included both stuff and storage sacks so you can bring your bag along and make sure it stays lofty when you're off on more summery adventures.

    • Pertex Shield 2L waterproof and breathable membrane
    • 30D nylon ripstop outer fabric
    • Pertex Microlight 30D nylon ripstop lining
    • 800-fill goose down
    • Cross-baffle construction
    • Wrap-around footbox
    • Down-filled draft collar and draft tube with hidden pocket
    • Storage and stuff sacks
    • Drawcord hood
    • Item #MAR00IA
    • Reviews
    • Q & A

    What do you think about this product?

    Have questions about this product?

    down to the nitty gritty.

    • Familiarity: I've used it once or twice and have initial impressions

    Technical specs
    Best Use
    Temperature Rating (F)
    -40 degrees (F)
    Temperature Rating (C)
    -40 degrees (C)
    Long - Left Zip: 5 lbs.
    Regular - Left Zip: 4 lbs. 8.9 oz.
    Pertex Shield 30-denier 2-layer ripstop nylon
    Zipper Location
    Insulation Type
    800-fill goose down
    Fill Weight
    Long - Left Zip: 50.19 ounces
    Regular - Left Zip: 47.23 ounces
    Pertex Microlight 30-denier ripstop nylon
    Sleeping Bag Shape
    Fits Up To (in.)
    Long - Left Zip: 78 inches
    Regular - Left Zip: 72 inches
    Shoulder Girth (in.)
    Long - Left Zip: 65 inches
    Regular - Left Zip: 63 inches
    Hip Girth (in.)
    Long - Left Zip: 63 inches
    Regular - Left Zip: 61 inches
    Stuff Sack Size
    9.5 x 19
    Stuff Sack Volume
    22.1 liters
    Compressed Volume
    Long - Left Zip: 19.9 liters
    Regular - Left Zip: 15.5 liters


    • Familiarity: I've put it through the wringer

    The waterproofing on this bag is incredible! Don't have to worry about your down getting wet when the tent condensates. Entirely too hot for anything above 20 degrees. When its mega cold you sleep like a queen!

    -46 F was our low

      I bought this bag 3 years ago with Backcountry, I have used it 3 years in a row in the BWCA for winter camping. I sleep in a normal winter tent, not a hot tent. This past weekend we went winter camping in the BWCA and the forecast was a high of -3 F and a low of -30 F. We camped for 3 nights, one of the nights got down to -46 F and I can truly say that I had zero problems staying warm the entire night. I wore 1 base layer of smart wool long underwear and a smart wool beanie stocking cap. I sleep in a MSR Fury tent(also purchased with Backcountry). I would highly recommend this bag to anyone looking to stay warm in any winter camping conditions.

      I've never been cold

      • Familiarity: I've used it several times

      I winter camp a lot in Northern Michigan, temps sometimes creep down to -20F on the coldest nights...this thing is toasty. Usually i won't even bring it out unless its gonna be at least 0F, in which I switch to my Big Agnes Stormking 0. The shell is amazing too as it's fairly waterproof, a good feature to have on a down bag. It handles condensation very well. It is very lofty and hard to fit in any stuff sack, but what can you expect, this is the bag most people take to Everest. Honestly unless you live above the arctic circle or are into mountaineering, you really don't need this bag, unless you're crazy and specifically try to camp on the coldest days every winter just to see if you can stay warm.

      I've never been cold

      No Such Thing as Too Cold

      • Familiarity: I've put it through the wringer

      Great baffle
      Great hood

      Bulky (Needs XL Sea-to-Summit eVac Dry Sack)

      Recommended Uses:
      Winter Camping

      Awesome bag. I used this bag for plenty of winter backpacking trips in Alaska, and I couldn't be happier. It has always kept me warm and comfortable. It's easy enough to vent if it's not too cold outside (I usually partially unzip at around 0 degrees). The baffles and collar work great, and I even found the hood worked well. The bag typically collects a decent amount of frost during the night when I use it, but it has never felt damp when I unpack it for the next night. I've used this bag down to -20, and I slept great in a base layer and a balaclava. My only real complaint with this bag is that the zipper has a tendency to catch the fabric, so it can be annoying to fully zip when you're tired and freezing. Still, definitely a great bag for anyone going somewhere seriously cold.

      Great for the unexpected

      • Familiarity: I've put it through the wringer

      I bought this bag not knowing what to expect on a 12 day trip from LA to Washington's peninsula in mid-May, meanwhile going through all the National Parks in between. I've used it with an ENO hammock and underquilt, a backpacking tent and inside the driver seat of my sedan. It's great at keeping me toasty without the sweat- in snow, in rain, overnight sleeping while sitting in a closed car, in cold north-american weather. I have no doubt that it'll be perfect for Alaskan climate as well! Waterproof and easy to take care of. Packable feature is a plus too, definitely will bring on a cold backpacking trip!

      Heavy for heavy duty!

      • Familiarity: I've used it several times

      Not the lightest sleeping bag, but it kept me nicely warm when it was -17 °Celsius inside my tent on almost 6000m elevation. We slept with 3 people in the tent and there was some condensation on the inside of the tent. My bad kept dry, even after I spilt tea on it, and woke up the next morning and didn't make it outside for throwing up (sorry for the detail... high altitude sickness....). It kept fine, easy cleansing on the outside and the bag doesn't smell funny after all the usage.
      I am 5' 8'' and in the regular size me, in my thinner down jacket and my clothes for the next day, innerboots and a few bits and pieces I didn't want to get too cold all fit in there fine (contact lenses, thermos, electronics). I haven't used it on a bivy, but I expect it to be perfect for that as well. NOT for summer camping, but worth the extra lbs.


      • Familiarity: I've used it several times

      This is one amazing sleeping bag, it's relatively light weight for as warm as it will keep you. The military equivalent, the (extreme cold weather bag) is almost twice as heavy and will soak water with the cotton canvas exterior.
      This bag breathes as well so no worries about sweating. There is also no toxic, noxious smell to the exterior fabric like so many others have that are made outside of the U.S.
      Buy it, you won't regret it!


      • Familiarity: I've used it several times

      Not much into to writing these, but do read them, ha. Not a hi-altitude climber but do play in the back country. Liked the idea of warm-no-matter-what, and comfortable sleep all around, willing to pack an extra lb of down. cwm delivers. Have spent a few nights on snow on neo-air pad under the stars, or falling snow a few times, had to vent the bag, no prob doing so. 3 day bkcountry snow camp in glacier last month, stellar. Had girlfriend along, left and right zipper cwm's, w bags zipped together to canoodle, exceptional comfort, again had to vent, no prob. both bags are longs, so gear went in her foot space, nice to have. made great sit-up eskimo wrap playing card game on snowy night as well. Inhales, lofts to advert 8-10" well, tho a little less so after a few dozen uses, expected. stuffs well in sack. color, workmanship is superior. will bcountry hike with these, kayak camp, snow camp, and have an excuse so may head to denali next month.

      add that zipper wants to snag so slow and steady. nice if it had cell ph pocket.

      closing comment, 20% off here is a steal in this bag category. Happy trails.

      Bomb proof

      • Familiarity: I've put it through the wringer

      Bought this last fall. It's seen plenty of use. The coldest I've tested it was -55F. And that was far north of the artic circle (north slope). I use it with my Exped downmat 9 LW and North face mountain 25 tent. It has never let me down. I got the 6'6 one so their is plenty of room for boot liners. I put my wet/frozen fask mask in the bag before bed and every morning it is warm and dry. This thing is incredible. Would not hesitate to purchase again if this thing ever kicked bucket. A product that I have and will continue to trust my life with.

      HI Beau. I am heading to Mongolia in a few weeks with this bag where I will be testing it night after night (for a month) in temps below -30º. I am a 5'2" female who weighs about 110 lbs and I am frankly super nervous about stuffing it in the stuff sack. I wrestled with it yesterday for almost 15 minutes and worked up a sweat!! Ha! How do you travel with it? It is so lofty (which is why I bought it), but I will be moving from camp to camp having to stuff it over and over. Any suggestions? Should I get a 20L compression sack? Or a rolltop dry bag? I am a photographer and carry a lot of other gear so I need to figure this out soon! Thanks so much!!! Jami


        Just got my cwm bag. Nothing negative or positive to write about the bag yet, but ill add another review when I put this thing to good use. ill upload a picture of it compressed in a 20L sea to summit compression sack here soon.

        Unanswered Question

        Good afternoon,
        I would like to ask you about the measures of the regular Marmot CWM Sleeping Bag -40 Degree Down. I am specifically looking for a sleeping bag of 160 cm long and good for winter camping (-20 Celsius comfort).
        I would really appreciate it if you could recommend me something.
        Best regards,


        Unanswered Question

        I'm a little over 6'1". Should I order a regular length, or would that be a bit too short?

        Unanswered Question

        Any idea what size sea to summit compression event sack to use for the regular length bag? A large?