How to Choose Sleeping Bags for Backpacking
NEMO Sonic -20 Sleeping Bag
$699.95
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Built to be the only bag you need from -20°F to 40°F, the NEMO Sonic -20 sleeping bag is warmer and more fine-tuneable than ever before. Time to start planning some big-mountain adventures.
Key Details
Fill
800-fill-power down
Weight
Long - Left Zip: 4 lbs. 3 oz.
Compressed Volume
Long - Left Zip: 13.4 liters
Temperature Rating (F)
-20 degrees (F)
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- Updated Thermo-Gills™ feature a multi-stage zipper system that increases the bag's usable temperature range and allows you to fine-tune your comfort while inside it
- Chevron baffle construction better compartmentalizes down, eliminating migration and keeping the down evenly lofted
- Upgrades include a redesigned profile and draft collar, plus bolstered draft tubes; offset zipper creates a thermally efficient seal
- Shell and liner fabrics are fully recycled to the Global Recycled Standard (GRS)
- Shell and liner materials are bluesign® approved
- 800-fill-power, PFC-free hydrophobic down retains warmth in extra-cold conditions
- Down is certified to the Responsible Down Standard (RDS)
- Toester™ footbox keeps feet warmer, provides a waterproof barrier against tent wall condensation and protects down from moisture while drying damp clothes inside the footbox
- Stretch construction at the knees allows for comfortable side sleeping
- Covered by the NEMO Lifetime Warranty
Imported.
Temperature ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth, since many different factors contribute to your comfort while you sleep. Backpacking bags are typically rated for temperature according to an independent testing protocol—currently International Organization for Standardization (ISO) 23537, though some older items followed European Norm (EN) 13537. Testing is based on a person wearing one base layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38.
Each bag then gets 2 ratings: 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. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
View all NEMO Backpacking Sleeping BagsEach bag then gets 2 ratings: 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. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
| Best Use | Backpacking Mountaineering |
|---|---|
| Tested Lower Limit | -20 degrees (F) - ISO |
| Tested Comfort | Unavailable |
| Temperature Rating (F) | -20 degrees (F) |
| Temperature Rating (C) | -29 degrees (C) |
| Weight | Long - Left Zip: 4 lbs. 3 oz. |
| Shell | Recycled nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | 800-fill-power down |
| Fill Weight | Long - Left Zip: 2 lbs. 8 oz. |
| Lining | Recycled polyester |
| Sleeping Bag Shape | Mummy |
| Fits Up To (in.) | Long - Left Zip: 78 |
| Shoulder Girth (in.) | 63 inches |
| Hip Girth (in.) | 58 inches |
| Stuff Sack Size | Long - Left Zip: 10.5 x 15.5 inches |
| Stuff Sack Volume | Long - Left Zip: 22.3 liters |
| Compressed Volume | Long - Left Zip: 13.4 liters |
| Gender | Unisex |
| Sustainability | Product meets the bluesign® criteria |
Buying Advice
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Most Helpful Favorable Review
Excellent Bag
JSchnite3 years ago
I just used this bag on a backpacking trip. I always get cold and wake up in the middle of the night, but not anymore, this bag is extremely warm. If you're not sure if you need a -20F sleeping bag, I would recommend getting this bag. The air gills work really well to regulate body temperature. All the little features that you don't think about until you're actually sleeping in the bag really stand out. This is the most well thought out and designed sleeping bag I have ever owned. WELL DONE NEMO!
JSchnite
23 people found this review helpful
Most Helpful Critical Review
Deep disappointment
Thea2 years ago
Extreme disappointment. This did not even keep my spouse warm at 18 degrees F, let alone -20f. He was wearing long johns, socks and a turtleneck. I found him in the morning in his light down jacket with the hood on, deep inside the bag. We’re seniors now but we’re experienced WI campers. Thouht TU is would carry us through life. Not so much.
Thea
22 people found this review helpful
Coldsleeper
A good bag for temps above 25 degrees Fahrenheit
2 years ago
I only give this bag 2 stars for two reasons. The first is that this bag is only comfortable to temps above 35 degrees Fahrenheit . Below 35 you will need to start wearing warm clothes. Even with warm clothes like a light/medium insulated down jacket and pants I don’t think most people would be comfortable below 15 degrees. The other issue is the zipper constantly catches the baffle fabric when zipping up the sleeping bag. It never gets stuck hard but catches multiple times when zipping up even when trying to keep the baffle out of the zippers’s way. If you are looking to camp in temps between 25-50 degrees then I would give this bag 4 stars.
Weight:175–200 lbs.
Height:6'0"
Yes , I recommend this product
JSchnite
Excellent Bag
3 years ago
I just used this bag on a backpacking trip. I always get cold and wake up in the middle of the night, but not anymore, this bag is extremely warm. If you're not sure if you need a -20F sleeping bag, I would recommend getting this bag. The air gills work really well to regulate body temperature. All the little features that you don't think about until you're actually sleeping in the bag really stand out. This is the most well thought out and designed sleeping bag I have ever owned. WELL DONE NEMO!
Age:35–44
Weight:150–175 lbs.
Height:5'9"
Yes , I recommend this product
Mike
Chicago, IL
Mountain Tested
2 years ago
I brought this on my expedition trip to Mt. Aconcagua in Argentina. I slept at elevations between 10,000ft and 20,000ft and with temperatures as low as -25f. Obviously it was too warm for me at the lower elevations but during blizzards and extreme temperatures, it did its job. At -25, you need to layer up and sleep with extra clothing, but not only did it keep me alive, I slept comfortably at that temperature. The tents has a lot of condensation and i would wake up with a wet and frozen bag on the outside. With the waterproof footboy and hydrophobic down treatment, I never had any issues with the moisture reaching my body or affecting the warmth. Definitely recommended for all of your winter/mountain adventures. If you're 6ft or taller, go with the long version so you have extra room to throw clothing at your feet so you have warm clothes in the morning
Age:25–34
Weight:175–200 lbs.
Height:6'1"
Yes , I recommend this product
Chris M Wisco
Wisconsin
Great design, not warm at all!
2 years ago
Used this for two weeks in Alaska. Thermorest below, plus horse pads. Long underwear, down pants and down jacket and blanket on top and still cold with 20 degree nights. Told Nemo about it and they said the temp rating is just a guide and everyone is different and they reference the maximum coldest rating the bag could perform, not what it would be comfortable at. Would’ve been nice to know that at purchase. Asked for a refund and they said they would be happy to uhelp me select a better sleeping pad and campsite haha! So their ratings are half truths and they don’t stand behind their product.
Age:35–44
Weight:175–200 lbs.
Height:5'9"
No, I do not recommend this product
Thea
Deep disappointment
2 years ago
Extreme disappointment. This did not even keep my spouse warm at 18 degrees F, let alone -20f. He was wearing long johns, socks and a turtleneck. I found him in the morning in his light down jacket with the hood on, deep inside the bag. We’re seniors now but we’re experienced WI campers. Thouht TU is would carry us through life. Not so much.
Zak
Maryland
Nemo's Sonic -20
4 months ago
Whenever you review a winter sleeping, it's important to include the users' entire sleep system. Half of your body warmth is lost through conduction from the ground. My winter system includes the Sonic -20, Cocoon's merino wool liner, Nemo's Switchback Sleeping Pad, Exped's Dura 8R, and an aluminum folding mat. I wear a dry sleep set of 250 weight merino wool base layers, fluffy mountaineering socks from Smartwool, and Turtle Fur's synthetic overhood. The Nemo Sonic -20 has a draft collar with a velcro attachment. If you don't connect the collar, then you won't achieve a full seal. Likewise, there's an inner draft baffle that runs the entire length of the zipper. If you rotisserie chicken and pull this inner baffle away from the zipper, the bag will lose heat. The gill vents feature inner and outer zippers. This gives you a total of four gill zippers to toggle for temperature control. Users who don't understand how the draft collar or zipper baffle works are going to have a bad time. You are hard pressed to find a better winter bag than this within the price range. The next tier of sleeping bags cost between $800-1400. My only complaint is that I wish there was a 900+ goose down version of the Sonic -20. The 800 FP duck down is heavy at 3-4 lbs.
Age:35–44
Weight:175–200 lbs.
Height:5'8"
Yes , I recommend this product
Defiantely not a playapus
MSP
Just fine
1 year ago
I saw the bad reviews, dudes. I have a 600 weight 0 degree bag, this weights the same. Fluff is what you are buying. Yes, you should sleep with some clothes on, also fluff up your bag before diving into it. I have not tried this bag since it's Sep, but really I don't care it's 800 weight down, I know what I purchased.
Height:6'2"
Weight:175–200 lbs.
Pluie
Always cold. Glad I bought it!
3 years ago
Seems beautifully crafted. Could really live up to its temperature rating, if tested.
Ermergerd
Texas
Great So Far
1 year ago
Great out of the box, but haven’t camped with it yet. Tested it on the couch, zippers work great. Started with the gills closed. Started sweating and getting too warm 40 minutes in. Opened the gills, inside and out, which made a big difference in air flow. I will update more after my October camping trip.
Age:35–44
Weight:150–175 lbs.
Height:5'9"
Yes , I recommend this product
Harlock
LA, CA
warm bag
1 month ago
Haven't had a chance to use it, yet, but you wanted a review. I had another Nemo bag but it wasn't warm enough so I got this one. I always seem to sleep cold. I did try a 0deg synthetic bag, but it was way too bulky so went back to down, plus it feels nicer. Fit check in bedroom was good and it seems to have more bells and whistles than I can understand.
Age:65–74
Weight:175–200 lbs.
Height:5'5"
Yes , I recommend this product
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