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Nunatak Arc UL 20 Three-Season Quilt Review

Nunatak Arc UL 20 Quilt Review

The Nunatak Arc UL 20 Quilt is a thoughtfully-designed, lightweight three-season quilt. While fairly expensive at $425, its features and execution make it worth every penny. There are a number of quilts out there that cost a good $150 less than this one, but many of them lack premium features such as a draft collar, differential cut, or an edge tensioning system. Nunatak quilts are also highly-customizable. They offer a variety of fabric, sizing, and pad attachment options. So, if you know what you want, and don’t mind waiting a couple of months for it, consider placing an order with Nunatak.

The Nunatak Arc UL 20 is overkill for shoulder season trips in a good way. It’s very warm in near-freezing temps wearing only base layers and isn’t too hot for those occasional 50-degree nights. Mine is also wide enough that it will accommodate all my bulky layers when I want to try and push it below freezing. Weighing just only 23.2oz, I can’t really imagine a trip where I wouldn’t bring the Nunatak Arc UL 20.

Specs at a Glance

  • Product: Nunatak Arc UL 20
  • Temperature Rating: 20 degrees, F.
  • Insulation: 14.5oz (411g) of 900 fill power goose down
  • Fabrics: 15d Pertex Quantum Shell, 20d taffeta liner
  • Weight: 23.2oz, (658g)
  • Dimensions: 70” length, 54” shoulder girth, 40” footbox
  • Footbox: Closed, box-baffle.
  • Attachment: Edge Tension Control System (ETC) and Removable pad attachment straps
  • Extras: Silnylon stuff sack, nylon storage bag, two sleeping pad attachment straps
  • For complete specs: Visit the Nunatak Arc UL Page

Down Insulation

This quilt comes stuffed with 14.5 oz of 900 fill power goose down. Compared to other 20-degree quilts with similar dimensions this is a pretty generous amount of down. This down comes with the Responsible Down Standard (RDS) certification. Nunatak also offers a Dry Down option for no extra charge. I chose good, old-fashioned untreated down for my quilt.

The 15d Pertex Quantum shell is a great balance of light weight and durability.
The 15d Pertex Quantum shell is a great balance of light weight and durability.

Shell and Liner Fabrics

The Nunatak Arc UL 20 comes stock with a blue 10D shell and black 10D taffeta liner but there are plenty of other options. They offer 7d water-resistant fabric for use on the foot section. Heavier, more durable fabrics are also available. When I think about buying a quilt—especially one I want to have in my life for a long time—I take durability into consideration. I’m sure the 10D fabrics are fantastic and allow for maximum lofting as Nunatak claims, but I opted for heavier materials at a very small weight penalty.

I chose the sage green Pertex Quantum 15D shell and the 20D black taffeta liner. This added about 1.5 oz to the overall weight of the quilt. The quilt would have weighed 21.7oz with the 10d materials, and mine came in at 23.2oz. I think this weight penalty is worth it for someone like me who plans on having a quilt for a long time. Shells and liners wear out faster than down. Down in a well-used quilt can keep lofting for a good 20 years! The high price tag of $425 also nudges me to prioritize durability.

The Pertex Quantum performed as expected in terms of water repellency. Condensation beaded on the shell near my face and where the foot of the bag scraped the wall of the tent every night. I shook what condensation I could off the quilt and stuffed it only slightly damp into the stuff ack every morning.

Sizing and Dimensions

I am 5’ 11” and 160 lbs, so I purchased this quilt with a 70” length, 54” shoulder girth, and 40” foot box. The length is perfect for my height. The shoulder girth, however, feels a bit wide for my preference. I feel like a shoulder girth of 52” would have saved a bit of weight while also allowing me to make the bag narrower when I really need thermal efficiency. As it is, when I adjust the edges until they are touching underneath me, I’m just barely starting to feel like I’m in a 59” wide mummy bag. I would probably prefer to feel this constriction before the bag is at its narrowest limit.

I spent a very cozy night in the Arc UL somewhere outside of Flagstaff.
I spent a very cozy night in the Arc UL somewhere outside of Flagstaff.

So, if I ordered this quilt again I might choose a 70” length, 52” shoulder girth, and 40” foot box. One nice thing about Nunatak is that I could actually do this! I would have to wait a couple of months, but that might be worth it for the absolute perfect fit.

All that said, the size I ended up with is ridiculously comfortable. It just might be slightly roomy for experienced quilt users of my height and weight who prioritize thermal efficiency, weight, and don’t toss and turn a whole lot, or who know how to toss and turn without opening up gaps along the edge of the quilt.

I feel it is important to also mention that this quilt comes with a differential cut. This means that the liner is cut smaller than the shell. This is important because it allows the down to loft much better than in a quilt without a differential cut. Keep this in mind when comparing quilts. Many of the less expensive ones do not have this feature.

Draft Collar and Closure

The draft collar consists of a down-filled tube of fabric, which when the neck closure is cinched, prevents drafts from coming in around one’s neck. This design is simple, light and effective. When using this quilt around freezing, the collar successfully keeps the warmth in and the cold out. Draft collars are available as an option on many quilts now because they’re such an important heat retention feature.

It's such an essential feature, I don't think I could convince myself to buy a quilt without a draft collar.
It’s such an essential feature, I don’t think I could convince myself to buy a quilt without a draft collar.

Shock cord runs around the neck opening and can be cinched using a cord lock on the side of the opening. The placement of the cord lock is very thoughtful as it prevents the excess shock cord from dangling in one’s face. The snap closure is located on small pieces of webbing protruding from the neck baffle. This makes them fairly easy to find during the night. The snap also holds very well. It’s not as burly as the double snap used on Katabatic quilts, but much more effective than the tiny hidden snap on the REI Co-op Magma Trail Quilt 30, which pulls apart at the slightest nighttime movement.

Sleeping Pad Attachment System and ETC

The quilt I ordered has both a Removable Pad Attachment System and what Nunatak calls its Edge Tension Control system (ETC). The pad attachment system consists of flat plastic buckles on the quilt that snap to their adjustable mates on pieces of webbing affixed to the pad. It is easily adjustable and the buckles are unobtrusive. They’re also placed strategically away from pressure points such as the shoulders and hips.

The Removable pad attachment straps in conjunction with the ETC basically ensure no drafts will ever disturb your sleep.
The Removable pad attachment straps in conjunction with the ETC basically ensure no drafts will ever disturb your sleep.

The Edge Tension Control system refers to a piece of shock cord that runs through tubes of fabric along the inside edges of the quilt. The shock cord can be adjusted using a cord lock where the edges of the quilt meet the foot box. I usually tension it slightly before getting inside, but it’s easy enough to reach down there and adjust it even while in the quilt. This used to be an optional feature, but  is now included with every Arc UL Quilt

Nunatak also offers Under Body Straps, Ultralight Version, which consists of two pieces of shock cord that run underneath one’s body, not under the pad. These are adjustable using cordlocks on each side of the quilt. This option probably saves a handful of grams. Either the Ultralight Version or Removable Attachment System can be used in conjunction with the ETC, or the quilt can be ordered with only the ETC. Your options are nearly endless at Nunatak.

Adjust the shockcord to snug the edges of the quilt under your body when temps start to drop.
Adjust the shockcord to snug the edges of the quilt under your body when temps start to drop.

I have used both the ETC and the pad attachment straps together when temperatures get closer to freezing. I don’t feel like it would be an exaggeration to say that it’s close to impossible to experience drafts when using both. This is due partly to the fact that my quilt is slightly wider than necessary for my body size. As mentioned above, I can pull the edges all the way together and still be comfortable. It’s possible that I might experience more drafts if I were to order a narrower quilt. But then I don’t know that for sure. I do know that the combination of the pad attachment straps and the ETC makes this quilt more effective at sealing out drafts than any other quilt I’ve ever used.

I’ve used a number of other quilts and I believe that Nunatak has by far the most comfortable, most effective, easiest to use pad attachment and draft-prevention system.

  • The REI Magma Trail Quilt 30 has bulky toggles that often slip and are extremely annoying when my hip rolls onto one of them. This quilt’s lack of edge tension also allows gaps to open whenever I roll from one side to the other.
  • The system used by Katabatic Gear seems like a close second to Nunatak with its elastic binding running along the edge of the quilt. The attachment system used by Katabatic Gear is very effective but more challenging to use than Nunatak’s. Once attached it is secure and easily adjustable, but getting it there is often a pain, especially with cold hands.

Temperature Rating

I have used the Arc UL 20 in temperatures ranging from 34 to 45 degrees F. At 34 degrees I wore base layers, didn’t cinch the neck baffle, or feel the need to make the quilt as snug as possible. Despite not taking it to 20 yet I expect it to be a pretty accurately rated quilt. By that I mean I will probably be comfortable to about 25 wearing base layers, fleece, and puffy jacket. That’s about what I would expect from a 20-degree quilt.

On a recent trip into the Mazatzal Wilderness, I didn’t exactly push the limits of this quilt’s rating, but I did get to make some important observations about quilt selection. The forecast said we would see nighttime temperatures in the low 40s most nights, so the Arc UL 20 was going to be overkill. But I can’t even begin to explain how amazing it was to have an overkill bag on this trip. The last two days of the trip saw sustained rain and daytime temperatures in the 50s. We experienced complete raingear failure and ended our days totally soaked. Stripping off cold, wet clothes and sliding into a 20-degree quilt at the end of the day was incredible. At only 23.2 oz, why not carry a little extra insurance on such trips? Because loft is going to decrease a little every day on wet trips, I almost always want to have an overkill quilt with me.

The snap is easy to find during the night and very secure despite its small size
The snap is easy to find during the night and very secure despite its small size

I expected the torso and shoulder area of this quilt to be loftier. The quilt is designed with a very poofy foot box, tapering to what appears to be a moderately poofy shoulder. This actually makes a lot of sense because it’s easier to add torso layers than it is to add leg and feet layers. At least for me. I always carry a puffy jacket or vest, and a fleece top, but I don’t often carry down pants or down booties. So Nunatak’s choice to emphasize loft in the lower part of the quilt is probably a good one. I’m just not used to it after having used a Katabatic Alsek for the last four years. The Alsek has more consistent-looking loft from toe to shoulder. I think my initial questioning around the down distribution in the Nunatak is primarily a visual issue, and I had to just get over it. I’m excited to take this bag into the 20s with a jacket and fleece and see if my prediction is right, that it’s made with upper-body layering in mind.

Comparable Top Quilts

Make / ModelWeightFill PowerFill Weight
Nunatak Arc UL 2021.7 oz90014.5 oz
Katabatic Gear Alsek 2221 oz90012.4 oz
Enlightened Equipment Enigma Custom 2020.19 oz95014.57 oz
Zpacks Solo Quilt 2019.1 oz95013.7 oz
UGQ Bandit 2018.42 oz95012.01 oz
Hammock Gear Premium Burrow Custom21.06 oz95013.52 oz
Therm-a-Rest Vesper 2019 oz90012 oz


I would highly recommend the Nunatak Gear Arc UL 20 for a number of reasons.:

  • The materials and construction are top-notch.
  • The combination of the ETC and the Removable pad attachment system are superior to any other quilts I’ve used.
  • The draft collar is an important feature and I wouldn’t recommend purchasing a quilt without one.
  • The fact that Nunatak has a variety of material and sizing options makes this quilt highly-customizable.

If you’re the type of backpacker who knows precisely what they want and you are willing to put in the effort to order a custom quilt, then this one might be for you. Nunatak is also very easy to communicate with, and they are willing to entertain all sorts of custom options. I exchanged a number of emails with Jan at Nunatak, and they were pleasant and communicative. This fabulous customer service experience is yet another reason to purchase a quilt from this company.  The only real drawback to this quilt is the high price: $425 is a lot, but it may be worth it for those who want a draft collar, differential cut, custom sizing, custom materials, and the amazing Edge Tension Control system.

Disclosure: The author purchased this quilt.

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  1. Oh yeah – the OG of quilts…:-). Good review. I had this same quilt for 10 years and loved it. It was very well made and true to its temp rating. I had mine down to about 25 degrees and it kept me warm as long as I burrowed and did not move. For this reason I had the long version.

    I say “did not move” because even with straps I always seem to get cold spots with quilts. I’ve switched to sleeping bags in very cold temps but love quilts in above 40 degree temperatures. I’m getting ready to try another brand of quilt but can give Nunataks only two thumbs up.

      • Original Gangster. It’s what us hoodrats call the most original properly working design.

      • Also can be old gangster.

      • I had to look this up the other day, too, Philip! We are approximately the same age and are beginning to qualify as Old Gangsters! (Waiting now for Grandpa to chime in!)

      • Somehow Grandpa missed this entire column and only got to it via link from the Packrafting Gear List post on 5/4/20.

        Grandpa never was a gangster but on many occasions he’s probably been called (mostly behind his back) an OG… Old Grumpster.

    • Curious what quilts have given you cold spots. I feel like the differential cut could help prevent that. Harder to push a knee through all the way to the shell with the inner fabric cut smaller than outer.

      • I have millennial brothers, and probably picked up OG from them. It is definitely a term of respect. I do think Old Gangster would make an awesome trail name, if not taken already! :-)

        I’ve tried the Nunatak, a borrowed Enlightened, and also tried making one myself (did not go well). My next one is going to be a Katabatic. I was leaning towards the Flex, but based on Ben’s differential cut comment, I may take a look at the Elite.

        I hope to take the quilt out with me later this year. I had to leave the AZT last week, but hope to finish it and the CT in the late Summer/Fall, which may provide good temps for the quilt.

      • You’ll like the Katabatic. I used the Alsek for a few years and it’s great. Definitely no cold spots.

      • FYI, the KG Flex’s now also have a differential cut. Have since 2019 I believe…

  2. Thanks Ben. It’s always good to get first hand referrals!

    • The Katabatic quilts are high quality, for sure, but I feel they are a bit on the narrow side even for my slim/normal body. My guess is that the somewhat shaped cut is intended to make up for this. The regular width Palisade I tried measured 48″ without stretching and pulling. Going to a wide was not possible due to shortages at the time, but I would recommend that for anyone bigger than a beanstalk.

      • It’s true that the reg Katabatic is narrow. That’s the main reason I switched to the Nunatak. The 52″ shoulder was fine for me, but the narrow hip-width was a problem. I found myself sometimes unable to easily switch positions during the night. And when my legs/hips are sore and tight from hiking all day, this was sometimes uncomfortable. I wish they’d just make the footbox shallower, like most other quilts. Start it a good 9″ further down maybe.

      • Thanks for the review Ben! Do you by chance know your chest measurement and/or over the shoulder measurement? I’m trying to figure out what width I should get on an ARC UL and having trouble figuring out what will work. I’m a 45″ over shoulder, 38″ chest.

  3. You mentioned the REI Magma 30 a few times and did not put it in your comparison chart. It is reasonably priced at $250. I can’t justify $450 for a quilt. Is the extra $200 justified?

    • This is definitely a step up in quality over the REI Quantum Quilt. But if you plan to sleep in 40 degree+ temps, I wouldn’t bother. The Quantum is more than sufficient. You really only need these premium features if you want to sleep in sub-freezing weather. That’s my opinion, but it may not be Ben’s.

    • Greg, I agree with Philip. Also, the Magma 30 has 9.5oz of down in it whereas the Arc UL 20 has 14.5oz of down in it. So they’re just in slightly different temperature categories. That said, the Magma is really a great quilt for the price. Plus it’s on sale right now. The only thing I absolutely hate about it is the snap.

  4. Nunatak is leading the charge in premium quilts! I much prefer my Katabatic pad attachment compared to my Enlightened Equipment (seems similar to Nunatak). But, I also much prefer the vertical baffles on my Enlightened Equipment compared to horizontal on the Katabatic. If I were to order a 20 deg quilt in the current market, I’d definitely go for Nunatak.

    Also – it seems Katabatic has increased the fill weight across all models, including the Alsek.

    Katabatic Gear Alsek 22 22.1 oz 900 13.4 oz $450

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