This post may contain affiliate links.

Thermarest Ohm 20 Hoodless Sleeping Bag Review

Thermarest Ohm 20 Sleeping Bag Review

The Therm-a-Rest Ohm 20 is a hoodless sleeping bag insulated with 900 fill power hydrophobic goose down that weighs 1 pound 6 ounces (652 g). It is box-baffled and has a full-length, two-way side zipper with a draft tube, a puffy draft collar, with a silky 10d nylon/ripstop shell. In warmer weather, the Ohm can be unzipped and used as a blanket or quilt and you can even join two of them together to form a two-person sleeping bag.

Specs at a Glance

  • Temperature Rating: 20 degrees Fahrenheit / -6 Celsius
  • Gender: Unisex
  • Insulation: 900 fill power goose down
  • Down Treatment: Nikwax Hydrophobic Down (PFC-free)
  • Responsible Down Standard: yes
  • Weight: 1 lb 6 ounces (1 lb 7 ounces – actual weighed/652 g)
  • Fill weight: 12.5 oz / 354 g
  • Length: 73″ (a long 79″ model is also available)
  • Girth: 62″ x 56″ x 35″ (shoulder girth x hip girth x footbox girth)
  • Packed Dimensions: 6.5″ x 8″
  • Stuff sack included: Yes, compression sack
  • Storage sack: Yes
  • View for complete spaces (including metric conversions)

A Hoodless Sleeping Bag

The Ohm 20 is a hoodless sleeping bag
The Ohm 20 is a hoodless sleeping bag

The Thermarest Ohm 20 is a hoodless rectangular sleeping bag which means you can sleep on your side, back, or stomach without being constricted by a mummy hood. The nylon liner and shell are silky soft and warm against the skin. The bag is insulated with 12.5 ounces of 900 fill power goose down that’s baffled internally, so there are no needle holes in the shell to leak cold air and it can achieve maximum fluffiness (loft).

While the Ohm 20 is rated for 20 degrees Fahrenheit, it has a comfort rating of 32 degrees. The 20-degree rating signifies the lowest temperature where men will remain comfortable, while the 32-degree rating signifies the lowest temperature where women or very cold sleepers will remain comfortable.

Draft Collar

The draft collar seals around your neck, upper back, and shoulders sealing heal inside the bag and preventing it from escaping.

The Ohm 20 also has a thick draft collar, something you mainly find on premium sleeping bags, that wraps around your shoulders, upper back, and neck to prevent cold air from leaking in from the top of the bag and keeps warm air that has been heated by your body from escaping. This is a must-have for a sleeping bag or quilt that you want to use below freezing. The draft collar closes a snap on the side of your neck and there’s a drawcord is used to tighten it. That drawcord is quite long, so you can reach it even when both of your hands are below the draft collar inside the sleeping bag.

Zipper and Draft Tube

A two-way zipper lets you vent the top or bottom of the bag
A two-way zipper lets you vent the top or the bottom of the bag.

The Ohm 20 has a two-way zipper so you can vent the feet by pulling it up from the bottom of the bag if they’re too warm, or the top of the bag if your torso is too warm, or both at the same time. You can also open the quilt completely so that it lays flat so two people can sleep under it, side-by-side. Alternatively, you can zip together two Ohm 20’s and make a complete two-person sleeping bag.

The cloth stiffener sewn alongside the zipper prevents it from snagging on the thin ultralight shell fabric
The cloth stiffener sewn alongside the zipper prevents it from snagging on the thin ultralight shell fabric. The down-stuffed draft tube below the tape folds over the zipper when the bag is closed and prevents cold air from leaking in.

The zipper has a cloth guard along one side which prevents snags, which is another premium feature. There’s also a tube of down insulation, called a draft tube, which folds over the inside of the zipper and prevents cold air from leaking in.

Thermarest Ohm 20 Sleeping Bag


Premium Sleeping Bag

The Thermarest Ohm 20 sleeping bag is a hoodless full zippered sleeping bag that can be opened like a quilt on hot nights. It is ultralight and ultra-warm, insulated with 900 fill power goose down and weighing only 1 lb 6 oz.

Shop Now

Hoodless Sleeping Bags vs Quilts

How does a hoodless sleeping bag like the Ohm 20 compare to a backpacking quilt and why would you buy one and not the other? Quilts, by definition, are open along the back so that your back is insulated by a sleeping pad (or an underquilt or pad if you sleep in a hammock), while a sleeping bag completely encircles you with insulation and draft protection. That’s the biggest difference between the two.

Note: Some manufacturers also call their hoodless sleeping bags: “quilt sleeping bags“, “blanket-style sleeping bags“, or “hybrid quilts“.

If you were to unzip the top of the Ohm, you could use it as a quilt, and its extra width would probably do a good job at blocking drafts along the sides of your sleeping pad. But I’d expect that you’d sleep a little colder because the down insulation isn’t as concentrated over your torso as it would be with a quilt with its narrower dimensions. The same would be true if you unzipped the Ohm to use as a top quilt in a hammock. That’s not to say that a hoodless down sleeping bag wouldn’t be usable in those circumstances, but it wouldn’t be as optimized as a quilt.

The Ohm 20 comes with a compression sack that you can use to shrink it down when packed. It gets pretty small compared to a regular down 20 degree mummy sleeping bag.
The Ohm 20 (middle) comes with a compression sack that you can use to shrink it down when packed.

Quilts have their downsides too, especially when you get below freezing and cold drafts become a bigger issue or you dislike faffing about with a sleeping bag attachment system. I hesitate to say that a quilt will always be lighter weight than a hoodless sleeping bag with the same temperature rating because there are so many different factors that contribute to gear weight. As with anything, which you choose comes down to personal preference and budget.

Personally, I prefer using a hoodless sleeping bag for sleeping on the ground down to about 30 degrees and a quilt when using a hammock. Below 30 degrees, I switch to a mummy sleeping bag and go to the ground, but that’s just me.

Hoodless Sleeping Bag Comparison Table

Make / ModelTypeZipperWeight
Therm-a-Rest Ohm 20Sleeping BagFull Length22 oz
Feathered Friends Tanager 20Sleeping BagNone18.6 oz
Feathered Friends Flicker 20 ULSleeping BagFull Length25.2 oz
Katabatic Gear Flex 20Sleeping BagFull Length23.9 oz
Zpacks Full Zip 20Sleeping BagFull Length21 oz
Enlightened Equip. Conundrum 20 Sleeping BagFull Length25.47 oz
Enlightened Equip. Convert 20 Sleeping BagFull Length26.45 oz


The Therm-a-Rest Ohm 20 is a super comfortable hoodless sleeping bag that’s ideal for people who prefer the wraparound comfort and security of a sleeping bag but dislike mummy hoods. It has all of the features of a premium sleeping bag, including 900 fill power goose down insulation, a draft collar, a draft tube, and a two-way snag-free zipper, just minus a hood. I think it’s a wonderful off-the-shelf option, although pricey if you prefer the wraparound security of a hoodless sleeping bag over a quilt.

Disclosure: Therm-a-Rest donated an Ohm 20 for this review.

SectionHiker is reader-supported. We only make money if you purchase a product through our affiliate links. Help us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.


  1. From a weight, price and features standpoint it looks almost identical to a FF Flicker (Flicker looks to be a little wider in the shoulders). Accurate or is there anything that differentiates? I’ve been waiting on availability of a Flicker (tall) for a while.

    • Definitely some overlap between the two. The flicker has a drawstring footbox, but also opens up completely like a blanket and I like their draft collar controls a bit better. The flicker also has continuous baffles which can be a good or bad thing depending if you like to move your down around, but you really can’t go wrong with either one. Thermarest makes really nice quilts/hoodless sleeping bags, such as this

  2. Is it really a fair comparison between the Ohm 20 and the Flicker 20? I don’t think FF tests to standards but are known to be closer to comfort than limit ratings. Looking at fill ratings, the Flicker has about 2 more ounces of fill and their fill is loftier. I suspect it would be warmer than the Ohm 20.

    • What I see is that the ohm is 2 oz lighter overall and meets the temperature spec because I know they send their bags out to be tested. In other words they keep you warmer with less weight. Plus, the Ohm is available and the flicker isn’t in a long. Inventory usually trumps no inventory.

  3. It is the versatile kind of bag I would use as I am a hammock person. I am a little disappointed that Thermarest used the name Ohm from ULA backpacks. Perhaps ULA should make a pack and call it Neo Air. Sorry I guess I’m just a grumpy old man with to much time on my hands.

  4. Looks like a terrific option.

    For me, the nod went to the Flickr because it’s made in the US. While some of Thermarest’s gear is made in the US, their bags / quilts aren’t. I do appreciate that TR is adhering to the RDS…as is FF.

    After using my Flickr 40 for many years and just being darn happy with it, grabbing a Flickr 20 was both an easy and a hard choice. I like trying things from different manufacturers…different approaches, different vibes, etc…but also like to buy stuff that I know works well for me and my tastes / style.

    And, ultimately, on-shoring manufacturing is important to me so I look to buy US-made stuff whenever I can. FF Tanager arriving tomorrow…so I really haven’t strayed far in terms of brands ;-)

  5. On the Ohm 32, I have seen opinions that it is very underfilled and hence sleeps much colder than limit / comfort indicates. What is your opinion on the Ohm 20 regarding this?

    • Seemed perfectly warm for me. Thermarest is one vendor I really trust when it comes to insulation fill to be honest. I know a lot about their testing process, both lab-based as well as in their cold room.

  6. I’m looking for reviews on the Ohm 32 bag, and can’t find much
    On them, would it be safe to assume it would be similar to
    The ohm 20 except for temperature rating? There is a sale
    At Rei on the 32 Ohm, and with gift certificates it is
    Very enticing, would appreciate your opinion.
    Thank you

Leave a Reply

Your email address will not be published. Required fields are marked *

Solve *