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Marmot CWM Sleeping Bag: -40F Down

$819.00 - $840.00

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    • Team Red/Redstone


    14 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?

    Trucker pat

      I'm a trucker and sometimes I dont like running my heat at night. I decided to try this sleeping bag to see if it really works. I was in Sioux Falls,SD the other night. The time was - 10 and I didn't turn my heat on. I sleep in underwear and a t shirt. I woke up 7 hours later very warm. It was freezing inside my truck. A 16 ounce bottle of water was frozen solid. I'm very pleased with this sleeping bag. It's worth the price.

      Solid bag; Comfortable at -30 F

      • Familiarity: I've put it through the wringer

      I have slept through two Mid-West winters in this bag in my car and in an unheated cabin. All the worries of staying warm at night are silenced with this bag. I use it comfortably between 40 degrees F (with the zipper open) and - 30 degrees F. I am 5' 10'', 170 lbs and I bought the long regular bag, which allows me plenty of space with room for clothes and a water bottle by my feet to keep them warm for the morning. I have a 45 lb border collie-Blue heeler and she will come in the bag with me most nights below freezing, with her, it is a tight fit but still comfortable enough to sleep through the night if we get pretty cozy. When storing the bag I leave it rolled up loosely, but when needed it can be stuffed into the available sack and attached to the outside of a pack. This was my first purchase of a below-zero bag and I am very impressed. I justified the cost because I saved 8 months of rent with the use of this bag, which easily made a return on the investment.

      Great Tool for Multiple Nights at -35

      • Familiarity: I've put it through the wringer

      I've used this bag over 20 nights in temperatures below 0F since purchasing it on a wim last year. Overall, I really like it and will use it in all my cold weather expeditions/adventures north of 66. Puffy, warm, roomy, tough, and reasonably priced. A luxury after a long, hard, cold day of skiing. The only issue I've had is condensation compressing the down on multi-night adventures when it gets really cold and perspiration freezes deeper in the down. I gave it a thorough testing on a crossing of the Finnmark Plateau in Norway last February. The bag performed flawlessly for the 5 day 4 night crossing. Temperatures never exceeded -20F. The bag kept me very warm all four nights when temperatures dipped to -35F. Moisture gets trapped from the inside by the very robust breathable shell and as I expected the down compressed a bit reducing the loft a couple inches by day 5. Some of this trapped condensation was probably worsened by me stuffing it each morning and putting it on the sled rather than an arctic bedding setup (as seen in the picture). Left the Piteraq home on this trip.
      However, the same shell prevents condensation from entering the bag from a wet tent ceiling after boiling the day's water. I would not recommend this bag for a long adventure in the arctic without a vapor barrier but rather a combo down/synthetic setup. It's perfect for week long adventures when temperatures dip below 0.
      Lastly, the bag fit is great. I'm 6'1" about 210 lbs and broad shoulders. The long version provides just enough extra length to stash boot liners in the bottom, while sleeping comfortably. The width works well for changing in frigid mornings or adding a layer if needed.

      Great Tool for Multiple Nights at -35

      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?