Tried & New: MontBell U.L. Super Spiral Down Hugger 0


0˚F // $519 (regular length) // 2 lbs. 5 oz. //

MontBell U.L. SuperSpiral Down Hugger 0
0˚F | $519 (regular length)
2 lbs. 5 oz. |

A good cold-weather sleeping bag should compress to the size of a cantaloupe; it should be true to its temperature rating; easy to get in and out of and cinch well enough to keep cold out and warmth in. Beyond that, a sleeping bag is pretty simple. MontBell, however, would beg to differ.

I’ve been using MontBell’s zero degree-rated U.L. Super Spiral Down Hugger for the last three winters and it’s anything but a regular bag. Its complicated name (let’s just call it the U.L.) belies even more complex construction. Unlike those of a traditional bag, the baffles of the U.L. spiral around your body at a 45-degree angle. That, combined with elasticized fabric and stitching and some classic tailor’s technique, MontBell says, makes the entire bag stretchy. And it is—the U.L. moves with me when I sleep making it both more comfortable and warmer, I think, than a regular bag.

From zipping in, the comfort of the U.L. is obvious. It isn’t restrictive—especially noticeable in the legs—and it’s stretchy enough that I can extend my arms almost fully outward. It feels light, unlike a winter-weight down comforter, but that doesn’t mean it’s cold. Because it’s stretchy, it hugs closely (as its name might imply), which I’ve noticed eliminates spots of dead air. I’ve slept comfortably in the U.L. on single-digit nights on ridge lines in New Hampshire’s White Mountains and toasty nights in western yurts and it will long be my cold-weather bag of choice.

+ The hood is extra lofty and there’s a full draft collar with dedicated face and collar cinches for keeping cold air out.
– It lacks a small pocket that, on other bags, is handy for storing earplugs, a headlamp or a late-night snack.
= True to its rating, ultralight, super compressible and far from confining. The U.L. takes cold-weather sleeping bags to dreamy level.



Big Agnes McAlpin SL
EN Lower Limit: 5˚F
Price: $360 (regular length)
Weight: 2 lbs. 15 oz.

Vertical baffles uniformly distribute body heat across the McAlpin, Big Agnes’s new, 700-fill cocoon that features DownTek insulation, a water repellant-treated goose and duck down.


Rab Neutrino Endurance 600
EN Lower Limit: 7˚F
Price: $499
Weight: 2 lbs. 7 oz.

The widest-fitting option of these four is an 800-fill down bag from British manufacturer Rab. The Neutrino has a water-shedding Pertex Endurance shell and a handy inner pocket placed on the generously sized draft collar.


Sea to Summit Alpine III
EN Lower Test Rating: -4˚F
Price: $649 (regular length)
Weight: 3 lbs. 8 oz.

Sea to Summit’s coldest-rated bag has a highly water resistant outer shell, wide footbox and inner pocket, and stiff “anti-snag lines” prevent the draft tube from getting caught in the zipper. The snuggest-fitting, but warmest, of these four.


Sierra Designs Zissou 0 Hi
EN Lower Limit: 6˚F
Price: $300 (regular length)
Weight: 3 lbs. 1 oz. 

Filled their proprietary DriDown—hydrophobic-treated feathers—Sierra Designs’s cold-rated Zissou is weatherproof and ultra affordable. The draft collar is somewhat thin and lacks a dedicated cinch but the bag packs small and is reasonably lightweight.



  1. Since it’s much more difficult for women to stay warm winter camping, it would be nice to know which of those bags kept a women warm…

    • Tyler Cohen says:

      Lynn–none of these bags are women’s specific, and were therefore untested by women. The warmest bag here is the Sea To Summit, both in its temperature rating, and its construction–the collar, draft tube and hood are the best of the bunch. Women’s bags are typically sized shorter, however, so the 6-foot (regular length) Sea to Summit might be a bit large. If you’re after a great fitting bag, the Mont Bell is unbeatable.

    • JoAnne Davis says:

      I’ve never been able to use a women’s specific sleeping bag because I’m 5’11” tall lol. There really aren’t that many long bags in women’s sleeping bags, and if there are, they still aren’t usually long enough for me. I do sleep very cold myself, and even the warmest of sleeping bags I tend to freeze in. I don’t do extreme winter camping, but I’m a wildland firefighter so sometimes if we’re in the mountains it can get very cold, even in the summer. I’ve had a couple different cold weather bags, and I’ve noticed anything that’s above 0 degrees won’t work for me. I always carry a Cocoon liner with me and wear wool long johns if I’m winter camping too. It also helps to have a winter season tent. Just my 2 cents haha. 🙂

    • I ran into that same problem as a 5’4” lady, i wanted a bag that had enough room for my boot liners, but not so big it would be difficult to warm up. Verdit? Western Mountaineering makes unisex ‘short’ 5’6” bags. the slim cut (YEP THEY MAKE A LARGER GIRTH SIZE AS WELL) is small enough for my SMALLER build and they have many temperature options, 5 degree, -10 degree, etc. Sizing ending up being an excellent excuse for me to spend the extra money on a *super Nice* bag!!

      And I agree with Joann, Liners can help your bag feel a bit warmer, though I LIKE THE PIECE OF MIND OF carrying a slightly heavier bag than say my hot blooded male ski/climbing partners.

  2. NortheastSoulRyder says:

    THANK THANK THANK YOU, AWESOME SNOW CATS!!!!! wE R BUILDING OUR first winter camping package. this was informative and really gave me a few places to start looking for the kind of bag i want. I am lucky enough to have an amazing Snow angel in my life that is more core then anyone i have ever met. WE ride 75 hard northeast days a year, living 6 hours from our season pass held mountain. hotels are killing us. the backcountrty/winter camping beckons. a couples specific site set up/ breakdown type article would really expedite our foray into cold smoke nights. I salivate at the idea of seeing the Adirondack High peaks by planks!!! THINK SNOW!!

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