How to Choose Sleeping Bags for Backpacking
Therm-a-Rest Parsec 0 Sleeping Bag
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Whether on an overnight snowshoe trip, a ski tour or just a quiet, off-season backpacking trek, the packable Therm-a-Rest Parsec 0 sleeping bag provides plenty of warmth for winter pursuits.
Shop similar productsKey Details
Fill
800-fill-power Nikwax Hydrophobic Down
Temperature Rating (F)
0 degrees (F)
- 20-denier recycled nylon shell is soft, durable and lightweight
- 100% recycled nylon shell and liner are certified to the Global Recycled Standard
- 800-fill-power Nikwax Hydrophobic Down™ absorbs 90% less water and dries 3 times faster than untreated down to keep you warm and dry in wet conditions
- Down is PFC-free and certified to the Responsible Down Standard
- Refined shape adds a bit of girth in the shoulder to accommodate more clothing layers while shaving up to 2 oz. off the previous version
- Heat-mapped, zoned insulation delivers an elite warmth-to-weight ratio by allocating insulation to where you need it and reducing it where you don't
- No-snag YKK® zipper eases entry and exit and prevents accidental tears
- Cinchable hood, heat-trapping draft collar and full-length zipper draft tube help keep heat in
- Down-lined Toe-asis™ foot pocket helps keep your feet warm in the dead of winter
- Improved—and optional—SynergyLink™ connectors strap to your sleeping pad to give you freedom of movement without shifting off the pad and losing warmth
- External zippered pocket stashes small essentials
- Quilt and blanket loops let you customize your sleep system by layering a Therm-a-Rest quilt or technical blanket for increased warmth (quilt/blanket not included)
- Compression and storage sack included
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 Therm-a-Rest 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 |
|---|---|
| Tested Lower Limit | 0 degrees (F) - ISO |
| Tested Comfort | 14 degrees (F) - ISO |
| Temperature Rating (F) | 0 degrees (F) |
| Temperature Rating (C) | -18 degrees (C) |
| Shell | Nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | 800-fill-power Nikwax Hydrophobic Down |
| Sleeping Capacity | 1-person |
| Lining | Nylon |
| Sleeping Bag Shape | Mummy |
| Gender | Unisex |
| Sustainability | Down certified to the Responsible Down Standard (RDS) Contains recycled materials |
Buying Advice
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Most Helpful Favorable Review
Fabulous Bag That Performs!
Captain Berz2 years ago
I took it out in 7 degree temperatures with industry certified thermometers and tested it out! I would not recommend Thermarest Parsec 0° Down Sleeping Bag below 5 degrees after my usage and testing. It might work at 0 degrees, but I can confirm a good night in 5 degrees. With space to add a small insulation layer to extend the bag rating a little! The Therm-A-Rest Parsec 0° Down Sleeping Bag is comfy, well thought out and has even warmth! Here are the results!
Air Temp: 7° Degrees
Starting Temp In Bag: 32.1° Degrees
5 Minute Bag Temp: 55.4° Degrees
10 Minute Bag Temp: 65.4° Degrees
15 Minute Bag Temp: 72.6° Degrees
20 Minute Bag Temp: 76.6° Degrees
25 Minute Bag Temp: 78.8° Degrees
30 Min Bag Temp: 80° Degrees
35 Min Bag Temp: 80.9° Degrees
40 Min Bag Temp: 81.6° Degrees
45 Min Bag Temp: 82° Degrees
Captain Berz
Harrisburg, PA
22 people found this review helpful
Most Helpful Critical Review
synergy link straps are too short for 25” pads
MartyS2 years ago
This is a phenomenal sleeping bag except one huge overlook by Thermarest! How do you make a sleeping bag with synergy link connector straps that don’t fit around your own branded 25” wide sleeping pads!?! How I’m the world does this make it out of quality control of a multimillion dollar business!?! The synergy link connector straps are necessary to keep the less insulated bottom part of the bag in contact with the inflatable insulated pad!
I contacted customer support for Thermarest and the answer I got:
“sorry we don’t make wide pad synergy connectors, it says in the product usage page they’re compatible with 20” wide pads and mattresses 3” thick or less.”
I’d only recommend the Parsec 0°f sleeping bag if you only use 20” wide pads or don’t care to use the straps!
MartyS
Northern Virginia
13 people found this review helpful
Customer Images
Juan G.
Great Sleeping bag, exceeded expectations in really harsh conditions
2 years ago
Winter camping in the Pacific Northwest is serious and dangerous if not well prepare, this sleeping bag worked better than expected pair with NeoAir XTherm R value 6.1, the temperature was19 degrees and I was literally hot to the point that I had to open the upper part of the bag to cool down, this is a zero degree sleeping bag so I know it will deliver if im at lower temperatures just fine. 5 stars hands down.
Originally posted on a Cascade Designs brand site
Captain Berz
Harrisburg, PA
Fabulous Bag That Performs!
2 years ago
I took it out in 7 degree temperatures with industry certified thermometers and tested it out! I would not recommend Thermarest Parsec 0° Down Sleeping Bag below 5 degrees after my usage and testing. It might work at 0 degrees, but I can confirm a good night in 5 degrees. With space to add a small insulation layer to extend the bag rating a little! The Therm-A-Rest Parsec 0° Down Sleeping Bag is comfy, well thought out and has even warmth! Here are the results! Air Temp: 7° Degrees Starting Temp In Bag: 32.1° Degrees 5 Minute Bag Temp: 55.4° Degrees 10 Minute Bag Temp: 65.4° Degrees 15 Minute Bag Temp: 72.6° Degrees 20 Minute Bag Temp: 76.6° Degrees 25 Minute Bag Temp: 78.8° Degrees 30 Min Bag Temp: 80° Degrees 35 Min Bag Temp: 80.9° Degrees 40 Min Bag Temp: 81.6° Degrees 45 Min Bag Temp: 82° Degrees
Age:35–44
Weight:200–225 lbs.
Height:6'0"
Yes , I recommend this product
Cofee_Break
Oakland New Jersey
Great bag until we had a warranty claim in 9/2024
8 months ago
Bought two of these early in 2024 and was very happy with the weight/warmth ratio. I used them on multiple backpacking trips, including a week on the JMT in late September when the nighttime temps were in the 20s. Kept us warm and were light to carry. One MAJOR downside to this bag: Thermarest which is owned by Cascade Designs, is no longer honoring warranties. We learned this when a zipper broke on one of the two. We filled out the proper forms online and even got an automated response that it was received, and someone would contact us. Nothing. Weeks passed, and resubmitted. No response again after the auto-receipt email. I then googled it, and it turns out that many others who have had a repair/warranty issue in the second part of 2023 have had the same Ghosting by Thermarest/Cascade Designs. Same exact experience that we have had. In summary, it is a good sleeping bag, but beware of any Thermarest purchase at this point, as there is no longer a customer service dept or warranty claim. I hope that I am wrong!
Age:55–64
Weight:175–200 lbs.
Height:6'0"
No, I do not recommend this product
Harpermitch
Chimney Rock, CO
Exceeded Expectations During Back Country Hunt
2 years ago
My first use of the bag was this week for six nights in the Colorado high country the third week of November 2022. Temperatures ranged from 0° to 18° At the coldest. Are use these in a wall tent This sleeping bag is lightweight. It compresses extremely well into the stuff sack provided. Zipper works great but did hang occasionally when zipping or unzipping from inside the bag…. Light weight sleeping bag material made it easy to “unsnag”. Using external zipper I experienced no snags. Able to easily roll from side to side with the oversized mummy design. 5’10” at 215 lbs. I used this bag in a wall tent. Slept on a cot with a sleeping pad with unknown R rating(not much if any). There were some cold spots under my midsection but was quickly remedied by placing a jackets between bag and pad. I slept comfortably each night. The water resistant down worked excellent. Each night Lots of condensation, and eventually ice formed from my breathing. I would hang the bag out each morning and it would dry quickly and the loft remained.
Age:45–54
Weight:200–225 lbs.
Height:5'10"
Yes , I recommend this product
MartyS
Northern Virginia
synergy link straps are too short for 25” pads
2 years ago
This is a phenomenal sleeping bag except one huge overlook by Thermarest! How do you make a sleeping bag with synergy link connector straps that don’t fit around your own branded 25” wide sleeping pads!?! How I’m the world does this make it out of quality control of a multimillion dollar business!?! The synergy link connector straps are necessary to keep the less insulated bottom part of the bag in contact with the inflatable insulated pad! I contacted customer support for Thermarest and the answer I got: “sorry we don’t make wide pad synergy connectors, it says in the product usage page they’re compatible with 20” wide pads and mattresses 3” thick or less.” I’d only recommend the Parsec 0°f sleeping bag if you only use 20” wide pads or don’t care to use the straps!
Age:45–54
Height:5'9"
No, I do not recommend this product
Luckyhorse
Salt Lake City
Best sleep in winter temperatures in a bag
3 years ago
I’m always prepared for the worst sleep when I camp, especially in colder temps. This bag is comfy and warm. I’m a side sleeper and had enough room in the small to sleep comfortably. I tried the regular which was too big. I also tried a sidewinder SL and liked the Therm-a-rest Parsec better. I’m buying a second Parsec in the 20 degree bag. I’m female for reference.
Age:35–44
Weight:150–175 lbs.
Height:5'4"
Yes , I recommend this product
Lsbs1234
Los Angeles, California
Best sleeping bag to actually keep you warm!
2 years ago
As a petite female I have never once been truly warm in any sleeping bag in low temperatures and I’ve owned many. I took this on a 3 day backpacking trip at high elevation and I was warm and toasty the entire trip. The size small was perfect for me. Enough room to sleep on my side but insanely warm! It’s also incredibly light weight which is great for backpacking. I got lucky and got this at discount at the REI garage store but honestly this bag is worth the price!
Age:25–34
Weight:100–125 lbs.
Height:5'1"
Yes , I recommend this product
Jacqueline S.
Super warm bag
2 years ago
I was skeptical as to whether or not this sleeping was going to get the job done as I am a very cold sleeper, but it it amazing. First time in a LONG time that I have not had to sleep in all of my clothes, a puffer coat, and beanie! Very comfortable, and I stayed so warm on the AT I was so glad I pulled the trigger on this bag! I highly recommend it. I have an ultralight thermarest sleeping pad and had no trouble fitting it inside the straps on the back of the sleeping bag but the standard size might not fit as many have stated. I have not tried it with a standard bag. Packs down tight and is small and light to carry. Will be taking this gem to Yosemite in June and I'm so glad to have it.
Originally posted on a Cascade Designs brand site
Allison H.
Cant beat it
7 months ago
Warm, comfortable, and packs down small. I use it for all my hunting trips and its great!
Originally posted on a Cascade Designs brand site
Matsuo
Excellent cold weather sleeping bag
1 year ago
A surprisingly light sleeping bag that kept me warm in 16 degree F (-9 C) nighttime weather. The snag-free zipper reduces snags, but does not entire eliminate this common sleeping bag problem.
Yes , I recommend this product
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