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.
Specs at a Glance
- Temperature rating: 0 degrees Fahrenheit
- Fill type: 800 Fill Power Down (duck)
- 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
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.
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.)
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.
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.
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.
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|
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.
- 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
- Left zipper only
Disclosure: NEMO provided SectionHiker.com with a sample sleeping bag for this review.Editor's note: Help support this site by making your next gear purchase through one of the affiliate links above. Click a link, buy what you need, and the seller will contribute a portion of the purchase price to support SectionHiker's unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.
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