Long Term Review: MontBell U.L. Super Spiral Hugger

Greetings hikers,

I have been waiting a while to write up this review, and over this past weekend I passed the 250-nights of use with a MontBell U.L. Super Spiral Down Hugger sleeping bag, and I told myself I would write up a review of this bag when I hit the 250-night mark.

The MontBell U.L. Super Spiral Down Hugger (herein I will simply annotate it as the ‘MBULSS’) is not exactly a sleeping bag that falls into the model of a SUL or XUL hiking setup. It is very much possible to carry this sleeping bag as a SUL hiker and it could be possible to do a XUL hike with the MBULSS #5 and maybe the #3 (but that would be really hard). So I realize that this sleeping bag might seem to be one of those sleeping bags that does not typically get reviewed by a SUL/XUL hiker, but if you are a SUL/XUL hiker you have probably come to learn the very valuable lesson that sleep comfort is almost as important as knowing your route and knowing how to maintain your core body temperature. So for me, having a sleeping setup that is above-par is a near-must. A little over 1000 grams of my 1800 gram BPW setup is devoted to my sleeping system (shelter & bag). Yes I could save 115 grams or so of weight (around 4 ounces) if I switched over to a ZPacks sleeping bag or an Enlightened Equipment Epiphany, but the simple fact is (for me) the comfort of the MBULSS is worth those three or four ounces. Hiking Lighter does not always mean hiking with the lightest possible gear in the world.

I have owned both the MBULSS #3 and a MBULSS #1 and have loved them both.

The #3 has an EN Rating of “40 comfort” and a “30(f) Lower Limit” and a “3(f) Extreme” rating. My thoughts on these ratings, as a cold sleeping, is that they are way off. I own the previous version when they were rated at 30(f) rather than 40(f) and I often found myself rather cold at anything under around 46. I made the mistake once of taking it out when it was going to be 30 and I pretty much froze all night, even with all of my clothing on. Whoever these “extreme” hikers are that can take this bag down to 3(f)… well, huge props to you guys!!

The #1 has an EN Rating of “26(f) comfort” and a “15(f) Lower Limit” and a “-19(f) Extreme” rating. I would say that these are a bit more accurate – again, I am a cold sleeper. The problem with the #1 is the bulk size of this bag. If you really stuff it, it can get down to around 7″ by 14″. As I almost never compress my sleeping bag, it can take up a rather large percentage of my ~1000 cubic inch backpack. The #1 also breaks the 2-pound limit, at 2.5 pounds, of which 1.5 pounds is 800 down fill and the other 1 pound is material. Compare this to the 17 ounces (482 grams) for the ZPacks 30(f) bag (remembering it is hoodless bag.)

I typically consider the 30(f) range the sweet spot in which sleeping bag to choose. Realistically anything under around 42(f) and I am cold. So a bag that can get me down to the 30(f) mark is a sleeping bag that I am going to shoot for, knowing that it should get me down to the freezing range, which is not all that common here in the Redwood Forest of Northern California, but it is very much possible to reach sub-freezing only an hour away from the Redwoods.

Perhaps the three biggest competitors to the MBULSS #1 is the Western Mountaineering AlpinLite, which is a 15(f) bag and is 31 ounces (1 lb 15 oz) (of which 19 ounces is down fill) and the Marmot Helium which is a 15(f) bag and is 38 ounces (2 lbs 6 oz) (of which 21.5 ounces is down fill) and the Nunatak Alpinist which is a 20(f) bag and is 22 ounces (1 lbs 3 oz) (of which 12 ounces is down fill).  [all bags based on 6′ length sizes]

The Nunatak is the only one of those three that I have not had the chance to try. Based on its specs I am not sure I would like using one – for the same reason that I do not like using the other two: they are not wide enough. I, like the vast majority of the people in the world, am a side sleeper. I am not only a side sleeper but when I get cold I very quickly go from being a side sleeper to being a fetal sleeper, and that requires a sleeping bug with a lot of width to accommodate the bent knees. And that is where the MontBell U.L. Super Spiral Down Hugger shines at.

It is no secrete that the problem with wide bags is that you end up sleeping colder, because of the larger amount of mass air inside the sleeping bag. The MBULSS solves this by being, well, a super spiral bag. When I am in a fetal position, it hugs my knees and bag. When I am in a standard side sleeping position, the bag hugs my knees and bag. If I happen to be sleeping on my back, the sleeping bag still hugs my sides. That is the awesomeness of the super spiral technology. There is very little dead-air space inside one of them. Perhaps the largest pocket of dead-air space of the entire sleeping bag is in the foot area, as it is not aggressively narrow in the foot region, which can be both good and bad. It is great when you want a bit of foot room, but I have also had my feet freezing a bit when I was pushing the limitations of the bag.

With over 250 nights of use on my #3 (and around 45 nights of use with the #1) I can definitively say that the sleeping bag has lost a fair amount of loft and thus warmth. I have washed it, treated it, and everything else I know of to try to bring back some warmth to the bag. If it falls below 50(f) I have found that the #3 is just not warm enough unless I put on a base layer of clothing or use a silk insert. It is rated at 40(f) so I would guess that it has lost around 8-10 degrees of warmth over the last 250 nights. I have never owned any other sleeping bag with this many nights of use so I am unaware of whether this is on-par with other bags or if this is rather poor performance. At this point the #3 is very little more than a summer time sleeping bag, or if I feel like carrying an additional 20-odd ounces of clothing to compensate for it. However as I previously mentioned the bulk of the #1 is significantly more than the #3 and in my backpack I have a hard time getting everything stuffed into it when I have to use the MBULSS#1. So I am more and more finding myself looking at one of the ZPacks sleeping bag and than a Nunatak Balaclava to compensate for the bag being hoodless. But, each time I do the numbers on the weight and the price, I just continue to think to myself that the pleasure of the pure comfort of the MBULSS sleeping bags are worth the bulk and the few extra ounces.


In accordance of Federal Trade Commission 16 CFR, Part 255: I hereby declare that the disseminated content within the review of this product(s) is free of endorsement(s) between myself and the manufacturer(s) of any product(s) disclosed herein and meets all FTC 16 CFR.255 compliance requirements.

5 thoughts on “Long Term Review: MontBell U.L. Super Spiral Hugger

  1. Hi John,

    Why the Nunatak Balaclava and not the Zpacks Goose Hood? The Nunatak is 4 oz with 800 down and the Zpacks is 1.3 oz with 900 down?????

    PLEASE explain…


    Also, I want to say that I got a Black Rock Gear down vest but I’m a little dissapointed with all the down it’s losing. Seems like the 7D fabric allows the down clusters to come out super easily. I just bought a Stoic jacket with Quantum Pertex fabric and NO down coming out of it at all! Your thoughts on this?


    1. Hello Fabian, thanks for stopping by.

      Regarding the hood: Simply choice for me. The Nunatak, while heavier, has more down than the entire zpacks hood (and therefore can be used in much colder conditions – remembering that the zpacks sleeping bag is a hoodless bag), additionally many hikers (myself included) believe that 800 down is superior to 900 down (because 900 down looses it loft very easily with just the slightest amount of moisture), it also has a snap closure on the front (thereby allowing it to be able to vent, should you discover your head getting a bit too warm (as well as making it easier to wear/talk while in camp/hiking/etc), and because I would prefer to have the Epic shell fabric, which would allow me to wear it for a longer duration while hiking in the rain/snow and not worry about the down getting wet. This choice of a hood is where additional weight for a piece of gear is less important to me than the usability of a piece of gear.

      Regarding the BRG Vest. Well it is 7D fabric, down pushing through it is to be expected. My Montbell U.L. Down Inner Parka uses 15D and it too leaks down. It is just a natural aspect of using material this light weight. You could probably wear the jacket for hundreds of days and have down leak out and still not loose loft. Two ounces of down is a whole lot of those little guys. Stoic uses 30D material in their sweaters and a 3-layer material in their bombshell jacket (probably over 100D). So, 7D verses 30D, is of course going to allow more goose down to leak through. But again, it could leak for years before it looses loft – and thus warmth – for the average hiker.

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