The NEMO Sonic 0 is an 800 fill power down winter sleeping bag that is cut wide around the knees and torso making it comfortable for back or side sleepers, much like NEMO’s spoon-shaped three-season sleeping bags. The Sonic 0 also features zippered vents down the front, called Thermo-Gills that allow you to vent the warmth of the sleeping bag up to 20 degrees without having to unzip the bag and introduce drafts. More on these below.
NEMO Sonic 0 Down Sleeping Bag
Warmth
Weight
Comfort
Features
Versatility
Excellent
The NEMO Sonic 0 degree down sleeping bag is a spacious cold weather sleeping bag that can be comfortably used by back or side sleepers. Tricked out with top of the line features such as a taped zipper, zipper draft tubes, and large draft collar, the Sonic 0 has innovative Thermo-Gills that let you adjust the warmth of the bag without cracking open the zipper and introducing cold drafts.
Specs at a Glance
- Temperature rating: 0 degrees Fahrenheit
- Fill type: 800 Fill Power Down (duck)
- Fabric:
- Exterior 20D Nylon Ripstop w/ DWR
- Footbox OSMO DT W/B w/ DWR
- Liner: 20D Nylon Mini Ripstop
- Length: Regular 72″, Long
- Weight: 3 pounds 2 ounces
- Compressed volume: 11 liters
Zipper
Like all good winter sleeping bags, the NEMO Sonic 0 has down baffles that run above and below the zipper to help seal out drafts when you zip it closed. The fabric that runs along the two-way zipper is taped with a fabric cover, a winter sleeping bag essential, preventing zipper snags or tears to the bag’s interior liner. Unfortunately, the Sonic 0 is only available with a left side zipper – I prefer having an option, and a right-hand zipper, myself.
Draft Collar
The Sonic has a beefy draft collar, a down baffle that lays across the top of your chest/neck and loops around your back to prevent the warm air surrounding your feet, legs, and torso from escaping when you move around at night; the so-called bellows effect. The tension and sizing of the draft collar is controlled by an elastic cord/large cord lock (independent of the hood), so you can adjust it while wearing thin gloves. The draft collar is closed inside the bag with velcro, also easy to use when wearing thin gloves (with a little practice.)
Hood
The mummy hood is well-insulated on top of your head and along the sides, but the front hood opening is shaped so you can lie on your side and not exhale into the hood. If there’s one thing I hate about winter mummy bags, it’s waking up in the morning with frost on the inside or sides of my sleeping bag hood. That’s not a problem with the Sonic 0 in my experience, though.
Dimensions
The interior space inside the Sonic 0 will delight people who prefer a wide sleeping bag with lots of space to wiggle around in at night. The dimensions of the 72″, size regular bag I tested are:
- Shoulder girth: 61″ / 155 cm
- Hip girth: 58″ / 145 cm
- Knee girth: 53″ / 135 cm
Horizontally-oriented baffles below the chest and over the knees along with stretch construction let you move around freely. There’s also plenty of room inside the Sonic 0 for storing boot liners, electronics, water bottles, and your stuffed animal so they won’t freeze at night, an important consideration when choosing a cold-weather sleeping bag.
Exterior Fabric
The exterior shell of the Sonic 0 is covered with a 20 denier nylon ripstop with a very good DWR that beads internal tent condensation on the surface of the bag and prevents it from wetting the down fill. The footbox is covered with NEMO’s proprietary waterproof/breathable fabric called OSMO, which is the same fabric they use on their waterproof/breathable bivy tents like the NEMO GoGo Elite. This is a nice feature for winter camping where you are more likely to experience internal condensation transfer between a tent and your sleeping bag, but it’s largely irrelevant if your most of your trips are just 1 night in length.
Thermo-Gills
The Sonic 0 sleeping bag has two zippers above the chest that you can open to shed heat, raising the temperature rating of the sleeping bag to 20 degrees Fahrenheit. This is useful if the temperature is warmer than 0 degrees or you want to make the bag warmer during the night, which is common as your metabolism slows and your body cools down during a long winter night.
The Thermo-Gills are not holes in the surface of the sleeping bag, as you might expect, but act more like cooling fins, allowing cold air to access the interior of the bag’s chest baffles and reduce the temperature of the air that they trap. They have a very noticeable effect on your warmth level when open or closed, but their biggest benefit is that they give you a way to shed unwanted heat without having to unzip the main zipper and introduce cold drafts.
Comparable 0 Degree Down Sleeping Bags
| Make / Model | Weight | Fill Power | Draft Collar | Price |
|---|---|---|---|---|
| Big Agnes Blackburn UL 0 | 2 lbs 12 oz | 850 | Yes | $500 |
| Big Agnes Orno 0 | 2 lbs 7 oz | 850 | Yes | $560 |
| Feathered Friends Ibis EX | 3 lbs 1 oz | 900 | Yes | $635 |
| Feathered Friends Murre EX Women's | 2 lbs 13 oz | 900 | Yes | $585 |
| Feathered Friends Snowbunting EX 0 | 2 lbs 13 oz | 900 | Yes | $599 |
| Marmot Lithium | 2 lbs 9.5 oz | 800 | Yes | $499 |
| Marmot Never Summer 0 | 3 lbs 3 oz | 650 | Yes | $279 |
| Marmot Ouray 0 Womens | 3 lbs 10 oz | 650 | Yes | $309 |
| NEMO Sonic 0 | 2 lbs 11 oz | 850 | Yes | $479 |
| REI Downtime 0 | 3 lbs 14 oz | 650 | Yes | $249 |
| Sierra Designs UL Nitro 0 | 2 lbs 8 oz | 800 | Yes | $379 |
| Sierra Designs UL Nitro 0 Women's | 2 lbs 7 oz | 800 | Yes | $379 |
| The North Face Inferno 0 | 2 lbs 14 oz | 800 | Yes | $519 |
| Western Mountaineering Kodiak MF 0 | 2 lbs 12 oz | 850 | Yes | $675 |
Recommendation
The NEMO Sonic 0 degree down sleeping bag is a spacious cold weather sleeping bag that can be comfortably used by back or side sleepers. Tricked out with top of the line features such as a taped zipper, zipper draft tubes, and large draft collar, the Sonic 0 has innovative Thermo-Gills that let you adjust the warmth of the bag without cracking open the zipper and introducing cold drafts. In addition to winter camping, the Sonic 0 is ideal for early spring, and early winter camping, when it can be difficult to find a sleeping bag that spans three-season and winter temperature requirements.
Likes
- Thermo-Gills allow you to vent excess heat without drafts
- Comfortable for back and side sleepers
- Spacious dimensions for winter gear storage
- Draft collar and zipper draft tubes
- Taped zipper prevents snags
Dislikes
- Left zipper only
Disclosure: NEMO provided SectionHiker.com with a sample sleeping bag for this review.
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Hi Phil, Douchepacker here. I’ve been eyeing this bag and Im wondering if this is a winner that you’ve continued to use?
Oh yeah. This one is a keeper.
Thank you Phil!
Review seems pretty much aligned with my experience. It is a good bag and a decent value, with a couple of caveats:
It has less fill than most other zero bags, and coupled with the higher volume that means it is not as warm and it takes more to keep it warm. Zero would definitely be pushing it without wearing other insulation in it.
Do you think that the 2019 update to the NEMO Sonic zero is worth the additional monies?
No – The 2018 model is a great bag. They added a couple of ounces too the weight in 2019, improving something that was perfectly good to begin with.
Sonic 0*F & -20*F are available 20% off on Campsaver Labor Day ‘one item’ sale. I like snow caves, tarps, and cowboy camping so I went with the minus 20. Kind of praying it’s not too warm for average nights.
I love my 10 degree Nemo bag, and have found that the high-quality down, “thermo gills,” large baffle at the throat and well-designed zipper make it easy to shed or trap heat in, depending on your need. While the bag is heavier and bulkier than ultralight options, I switched from a quilt because I found a quilt too drafty for squirming around while I sleep. In really cold weather, there’s enough room in the bag to wear your puffy, down socks, etc. I especially like the twill tape for the zipper, since I once had a serious problem with a zipper jam on a North Face bag in very cold conditions. Of course, I bought the Nemo bag after reading SectionHiker’s review and reader comments.
Finally tried out my Nemo Sonic minus 20*F bag on the back porch, with both gill slits open I was very comfortable at plus 20*F with the bag fully zipped up but the hood drawstring loose.
I couldn’t go warmer than 25*F without fully unzipping and using the bag as a quilt.
I have some lingering doubts about cowboy camping at minus 20*F without at least a bivi, or a snow wall to block the wind.
My style is a little different perhaps but if you haven’t seen a winter moon cross the night sky from a snowy mountaintop, then you’ve missed one of nature’s best “limited engagements”.
Been using the original for years. Love I, highly recommned.
I’m considering this bag, the WM Kodiak or FF Ibex, but don’t have a store where I can see all three in person. Do you have any thoughts on the Sonic vs the others?
I’d go with the Ibex. FF makes the best bags. Period.
I’m looking into this bag and wanted to know how well it works for side/stomach sleepers. I bought a Zenbivy, and I love how comfortable it is, but it’s huge, and the sleeping pad is even bigger and doesn’t pack down well. What are your thoughts for side sleepers? Can you move around inside easily? Also, can you fit a pillow in the hood, looks tight?
Side sleepers yes. Pillow, no.