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Nunatak Arc Ghost Sleeping Bag REVIEW

Innovative variable girth top bag that weighs under a pound and is rated to freezing.

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by Doug Johnson | 2005-10-18 03:00:00-06


Nunatak Arc Ghost Sleeping Bag REVIEW - 2
Sleeping out in the Nunatak Arc Ghost.

Publisher's Note: Variable girth bags have long been a part of's history. The variable girth concept was the subject of BPL's very first editorial that was released prior to the launch of the site, way back in April 2001, before any variable girth bags were made available on the commercial market. We acknowledge subscriber Don "Photon" Johnston, who was as instrumental as any individual in bringing the variable girth concept to market. Read more information about the history of the arc cross section variable girth design.

At just 14.9 ounces for a size long, the Nunatak Arc Ghost is among the lightest 32 °F (0 °C) rated bags on the market. It achieves this light weight through its simple, effective design: it features a closed foot box but an open, zipperless back. The back can be closed with two adjustable straps and a snap-closed neck with cinch cord, or it can be left open and used as a blanket. Not just lightweight, this "Variable Girth" design increases versatility, allowing the bag to be used within a wide temperature range by adjusting its circumference. A warm hat, hood, or balaclava is needed in colder temperatures as no hood is provided with the bag. The Arc Ghost is an innovative and well-constructed bag that is a good value, especially when considering its weight and versatility.

In Brief

  • Extremely light at 14.9 ounces (423 g) for size large
  • A lighter weight and narrower version of the Arc Alpinist
  • Warm enough for cooler temperatures when using a warm hat and extra clothing
  • Two body straps and a neck snap and cinch secure the bag to your body
  • Variable girth, can be cinched tight or unclipped and used as a quilt
  • Foot box is warm but a snug fit
  • Open back takes some getting used to, but is effective when sleeping stretched out on your back or stomach





Arc Ghost


Top bag

Size large tested

Small fits up to 5'4" (163 cm), Medium fits up to 5'10" (178 cm), and Large fits up to 6'4" (193 cm)

Size large tested

Backpacking Light measurement
in (cm)
Manufacturer specification
in (cm)
Shoulder girthvariable 44–62 (112–157)46 (117)
Hip girthvariable 42–52 (107–132)43 (109)
Foot girth34 (86)34 (86)


Backpacking Light measurement 14.9 oz (423 g) size large; Manufacturer specifies 16 oz (454 g)

  Fill Type

800+ fill power goose down

  Fill Weight

9 oz (255 g) size Large (tested), 8 oz (227 g) size Medium, 7 oz (198 g) size Small


Backpacking Light measured single layer loft 2.25 inches (5.7 cm)

  Manufacturer's Rating

32 °F (0 °C)

  Outer And Liner Material

0.85 oz/yd2 nylon with Teflon DWR




No (two adjustable straps and snap with cinch at neck)

  Model Year



$278 (small), $307 (medium), $340 (large)


Nunatak Arc Ghost Sleeping Bag REVIEW - 1
The Nunatak Arc Ghost uses a closed foot box, two body straps, and a collar snap with bungee cinch strap to hold in the heat.

The Nunatak Arc Ghost is a simple, effective, and extremely lightweight (14.9 ounces for size long) solution to sleeping in temperatures above freezing. It is a zipperless bag that has a closed foot box and an open body that insulates on the top and sides. During warm temperatures, the bag can be draped over you like a quilt. When the temperature gets colder the sides of the bag tuck underneath your body and two body straps cinch to secure the bag beneath you. This "Variable Girth" system allows you to adjust the circumference of the bag based on temperature or the amount of clothing worn inside the bag. The neck of the Arc Ghost closes with a snap and has an elastic drawstring at the center. It does not have a hood so a warm hat or balaclava is necessary in colder temperatures (Nunatak also has a separate Down Balaclava available for full head and neck coverage).

The Arc Ghost is sufficiently sized to fully wrap over my broad shoulders and the bag comes together at the back with about a 6 inch uninsulated gap with the straps fully tightened. It is designed to be used on top of a sleeping pad, unlike the Western Mountaineering Pod bags, which attach to the pad with straps, allowing the Nunatak bag to be closed almost completely. (While it is possible to attach the straps beneath a pad, this option is not as warm.)

Sleeping in the Nunatak Arc Ghost takes some getting used to. Rolling over as you might in a traditional bag exposes your back to the cold air. However, I quickly learned to hold the bag in place when rolling over to keep the bag from shifting with my body and it soon became second nature. While the bag works best for back sleepers, I am typically a stomach sleeper and the bag worked fine in this position as well. When sleeping on your side, it's difficult to keep the sides of the bag properly tucked under your body.

I never missed not having a zipper on the Arc Ghost; the strap system was easy to adjust and I had no problem getting into and out of the bag. If things got warm or I needed to get up quickly, releasing one snap and two small quick release buckles were all it took to open the bag completely. The two straps and top snap do a good job of keeping the bag evenly pulled under your body. However, there were times that gaps formed, especially when curled up. The main problem area was in the upper back between the top strap and the neck snap (a 29" space in size L). A third cinch strap would add a little weight but would help to avoid gaps for active sleepers like myself - especially in this larger size.

The bag is cut trim for a high degree of heating efficiency per ounce but there is sufficient room for me to wear insulated clothing inside and still have full coverage over my sides and shoulders.


Nunatak Arc Ghost Sleeping Bag REVIEW - 3
The Arc Ghost provides plenty of coverage under my back, even with the straps loose.

In the field, the Nunatak Arc Ghost provides a similar level of comfort to other bags with a comparable manufacturer's temperature rating. However, it is difficult to fully turn over inside the bag without letting some cold air in. This bag is much better for back or stomach sleepers; those that sleep curled up on their sides may have a difficult time avoiding gaps under the body.

Without a hood, the Arc Ghost relies heavily on choice of headwear for warmth in colder weather. On one night when temperatures approached freezing (the bag's temperature rating), I slept cold because I only had a thin fleece cap. On later trips, using a warmer hat in similar conditions made the bag much more comfortable to use; a warm down or synthetic hat that fastens underneath the chin or a balaclava are essential when pushing this bag to its limit. A lightweight bivy also helps control drafts, increasing the bag's versatility. When the weather is warm, however, the hat and bivy can be left at home and you can sleep comfortably with the bag simply draped over your body. With the right combination of accessories for the conditions, I found the Nunatak Arc Ghost to be quite comfortable in a wide range of weather conditions. It is also among the lightest bags available at this temperature range.

The Nunatak Arc Ghost is constructed with rectangular baffles that are well-filled with 800+ fill power goose down and provide 2.25 inches of loft on the top. I experienced no problems with down shifting in the baffles during testing.

Missing from this review (and for all sleeping bag reviews published here, for that matter) will be an assessment of whether or not the sleeping bag performs adequately at temperatures near its manufacturer-reported temperature rating. Click here for the complete Backpacking Light Position Statement on Sleeping Bag Temperature Ratings.


Nunatak Arc Ghost Sleeping Bag REVIEW - 4
The Nunatak Arc Ghost works well when sleeping stretched out on your back or stomach; it tends to leave gaps underneath when side-sleeping or curled up.

The Arc Ghost is a custom bag that is available in three different fabrics, a variety of colors, with overfill, or any other modifications you like (for an additional expense, of course.) The bag I tested used the 0.85 oz/yd2 nylon with Teflon DWR coating, which is the lightest fabric option available. Despite its weight, the fabric showed no wear during testing and only passed a couple of feathers. The DWR coating shed water easily and wasn't affected by many nights on the trail. Craftsmanship on the bag is excellent with seams folded in along the exterior edges for extra durability. The thin strap buckles did not break when stepping on them and with no zipper to jam, this bag should prove to be very reliable.


This is an extremely light bag that is well constructed and has good loft. At $259, $283, and $307 for size small, medium, and long, respectively, the Nunatak bag is not cheap but is competitive with other manufacturers. When you consider the versatility of the bag, it is a solid value.

Recommendations for Improvement

The changes I would like to see in the bag are:

  • A third strap added to the bag, at least in the size long (this is available as a custom option)
  • A lighter weight and less expensive hat/hood option for three-season use (the Nunatak Down Balaclava weighs 3 ounces and costs $99)


"Nunatak Arc Ghost Sleeping Bag REVIEW," by Doug Johnson. (ISSN 1537-0364)., 2005-10-18 03:00:00-06.


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Nunatak Arc Ghost Sleeping Bag REVIEW
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Ryan Jordan
(ryan) - BPL Staff - MLife

Locale: Greater Yellowstone
Nunatak Arc Ghost Sleeping Bag REVIEW on 10/18/2005 22:09:31 MDT Print View

Companion forum thread to:

Nunatak Arc Ghost Sleeping Bag REVIEW

Phil Barton
(flyfast) - MLife

Locale: Oklahoma
Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/19/2005 05:50:46 MDT Print View

The Arc Ghost looks very interesting. Am I the only side sleeper in the field? What are the experiences with a top quilt for those that are side sleepers? Is the variable girth idea only for those that can sleep comfortably on their back or stomach?

Inaki Diaz de Etura
(inaki) - MLife

Locale: Iberia highlands
Re: Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/19/2005 06:15:47 MDT Print View

I usually sleep on my side and I have an Arc Special (like the Ghost but wider, as wide as the Arc Alpinist) and I'm fine. I've noticed that turning inside the thing without inducing drafts starts being tricky when the bag is cinched tight (because the bag tends to move with the sleeper). I don't know if I'd be confortable with the Ghost's girth. There's a reader's review on this one you may find useful where the girth issue is addressed.
I can understand it's better suited for those who sleep on their back or belly but I think it's fine for side sleepers too.

Douglas Meredith
(dougmeredith) - F
Great bag for a hammock on 10/19/2005 06:17:50 MDT Print View

I have this bag and it works great in a hammock. I used it this spring in a tent and was quite cold. I had a lot of trouble with drafts as I tend to roll around a lot. This isn't a big problem in the hammock, as you can't really roll too much, and the sides of the hammock serve to keep the bag tucked in.

The straps are very fragile. One of the buckles broke the first time I used it. One of the straps is now ripped out; I think the cleaning lady got it with the vacuum cleaner (I keep it under a bed). This isn't a big deal to me as I don't use the straps in a hammock.

The neck closure works very well.


Mark Verber
(verber) - MLife

Locale: San Francisco Bay Area
Re: Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/19/2005 07:54:54 MDT Print View

I am a side sleeper. I haven't had problems with drafts. I had had slight problems with my hip creating a cold spot when I am at the comfortable limit of the quilt. Redistributing the down, or placing some clothing item on my hip takes care of the problem.

I colder weather I typically run the straps under my sleeping pad, so when I move and shift I am typically not generating a draft.



Locale: Pacific Northwet
Re: Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/19/2005 08:40:44 MDT Print View

I am a stomach/side sleeper. I own an arc-x, which is basically a ghost but dimensioned like and arc alpinist. (It has a girth of 55 inches vs the ~45 inches of the ghost). I have no problems side sleeping with this bag.

I also have an old Golite fur 1 quilt, which is a synthetic quilt with footpocket very similar to the nunatak bags. This quilt has a girth of about 46 inches and while it works for side sleeping it is a little more difficult to prevent drafts with this bag when side sleeping.

My advice, if you wanted to get a ghost would be to specify some additional girth to the bag. Nunatak bags are pretty much custom bags anyways. Adding 10 inches of girth at the shoulders would add minimal weight to the bag but make it much more useable.


Alex Orgren
(big_load) - F
Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/19/2005 13:10:21 MDT Print View

It seems possible to use this to extend the temperature range of an existing bag. Does anybody do this? Does the top bag go inside or outside (inside looks better to me)? How much would it add to the range? Unless it's at least 25 F, this probably isn't a cost-effective approach.

Pedro Arvy
(PedroArvy) - MLife

Locale: Melbourne
Too narrow on 10/20/2005 17:52:10 MDT Print View

As I said in the reader reviews

Pros: Lots of loft for the 400 grams of total weight. More than a WM Highlight for instance.

Cons: Too narrow. Way too narrow to sleep in for me and I like sleeping bags people normally say are too narrow. When you roll the bag "follows you", exposes the base and in comes the draft.

I also have the Arc Alpinist but the Ghost is a very different bag. It is MUCH narrower. I agree with Ryans rating, with overfill, the Alpinist is a 4 and the Ghost is a 2. It is useable, but very uncomfortable. I would also rate the bag to 40, not 32, but I do that with every bag.

Courtney Waal
(d0rqums) - F
Re: Nunatak Arc Ghost Sleeping Bag REVIEW on 10/20/2005 19:31:31 MDT Print View

I just got mine a few weeks ago and haven't gotten the chance to test it to the limits of the temperature range, but I feel like I've gotten a good sense for the bag.

-It's WARM. It easily has more than 2 inches of loft and the footbox seems to have more poof to it than comparable bags. Since the baffles are continuous, you can scoot the down to the top or bottom of the footbox where you need it. This makes it better for sleeping with your feet hanging off of a UL-cut sleeping pad.

-My custom shorter-than-medium (I'm 65in tall) is long enough for me to point my toes and still have sleeping bag over the back of my head or up to my nose, depending on position.

-I can put on my poofiest jacket and still be able to cinch the straps all the way down without any apparent compression of loft. It's wide enough to serve as a bag for two very cozy people in an emergency (think puppy pile- one laying on stomach and the other angled and somewhat over them).

-I don't get sweaty because I can shove whichever body parts are too warm out without waking up. I like the economy of getting one bag that will carry me through four seasons in the south.

-Can be worn as a cape with the neck tightened and the straps around the body- order it in red to be a lobster for halloween.

John Chan
32 F rating ok if.... on 10/23/2005 07:12:01 MDT Print View

You cinch up the quilt "just so" where there is 0 airspace but you haven't compressed the loft.

I own a semi-custom medium (cut for 67" stature) in microlight and 0.85. I've taken the bag down to 28 F in combination with other sleeping system items. This weekend the bag went down to 30 F using this combination:

1. Quilt
2. Montbell UL Breeze Dry-tec overbag
3. BMW Vapr Bivy

I was very cozy and my feet took no time to warm up at all. Best of all, in the morning I observed that the dewpoint was at the sil-nylon bottom (and to a minor extent on the quantum top) of the bivy and the interior of the overbag managed to stay completely condensation free (no clammy feeling on the PE membrane).

When I ordered the bag last year Tom Halpin @ Nunatak informed me that it had a standard 2" baffle height with no differential cut. This seems to work in most situations but a differential cut would've been useful for staying warm in my hammock last week. That said, you can probably spec a differential cut on on the Ghost with the quantum fabric outer without weight penalty but it will cost.


kevin davidson
(kdesign) - F

Locale: Mythical State of Jefferson
Ghost and differential cut on 10/23/2005 09:22:01 MDT Print View

Tom Halpin of Nunatak believes that a differential cut is wasted on the very light bags--you would have to talk to him about why.

Scott Jones
(Ultimate2) - F
Nunatak Arc Ghost Sleeping Bag Review on 05/05/2007 23:28:46 MDT Print View

The differential cut debate has always been there. Holubar down sleeping bags did not have a differential cut, but no one ever complained about getting cold in one. In fact the classic Holubar Expedition sleeping bag that I have in mint condition has just as much loft even today as a Westerm Mountaineering Bison or Marmot CWM etc. It is just a lot heavier because it is stuffed to the gills with 550 goose down which was the best available way back then.

I would be more worried about the width of the bag. Sounds like the extra money should be spent on widening the bag so it will cover you properly.