Review of Montbell UL Super Stretch #4 Sleeping Bag

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    Mitchell Keil


    Locale: Deep in the OC

    I am 6 foot 3 inches, weigh 175 age 56 sleep fairly warm and would classify myself as a lightweight (under 30 lbs skin out) packer.

    I bought the Montbell UL Stretch #4 bag Long about 2 months ago and have used it 4x.

    It weighs 1 lb 7.5 oz in a integral design XS compression stuff sack. It comes with a muslin storage bag and a very light stuff sack that has two draw strings with the idea that you would stuff it to the outer one and then cram it down to the second creating a “sort of” compression sack. It really does not work that well at doing it so I substituted the original sack for the Integral one and that one really cranks it down to about the size of an obese 1 quart nalgene bottle.

    The bag is exceptionally well made although somewhat rough when compared to, lets say, WM standards. When you open the bag up and turn it inside out the seam along the inside opposite the zipper is french seamed but exposed. The rest of the sewing is very good and tight. It has elastic baffles inside and out and top and bottom. They really hug the sleeper making for a much narrower bag in appearance than it really is. The ballistic air core 15 fabric is tight and does not seem to allow any down to escape and the DWR is adequate to ward off most accidental moisture. I would not want to expose it to anything more than the occassional spill or drip from tent condensation. I also would not recommend dragging this bag on the ground or drapping it over any spikey bushes to air out. The draft tube is adequate to the task of keeping cold air out of the bag but the stiffener used to keep the zipper from snagging is not up to the task. I have repeatedly caught the zipper in the fabic and struggled to get it zipped up because the fabric is so lightweight. (Thank God it so elastic and stretchy). There is additional zipper tape that is a part of the actual zipper which serves as an additional stiffener and would work but for the softness and lightness of the bag’s fabric. The zippers are lightweight, non-locking and there are two of them. The velcro tab at the top of the zipper run closing the bag is not properly aligned and takes some messing with to get it to properly catch and not scratch you during the night.

    Now that I have detailed some of the less attractive things about the bag, I want to get to the reasons why I really love this one. I toss and turn at night and almost always sleep on my side. This bag is a dream for that reason. It allows me to roll around and stretch as the name implies and still keep the bag’s inner surface close to my body. I can stretch out, angle my legs like a 4 under me and perform all manner of contortions and still the bag’s elastic baffles keeps it from losing warm air or creating clod spots. I had the bag out at 7,500 feet in Yosemite last week on a clear cold night when it got down to 32. I was fully exposed having rolled back my Sarvis tent canopy to look at the stars. I slept warmer and more comfortably than I can remember in an essentially summer rated bag. I wore my REI silk long johns and top — that was it. No cold spots toasty warm. Might as well have been home in bed it was so comfotable.

    I must say I was really concerned that this bag would deliver. It has very little down and yet lofts to about 4.5 inches to 5 inches.(Hard to tell with the elastic baffles). Each compartment is sealed off in a construction Montbell calls multi-box. Top and bottom have these squares of quilting about 6 inches on a side that each hold an amount of down. There is no continuous channelling with this bag but I have found that this construction allows the packer who tosses and turns or sleeps on his side to benefit from down that never shifts. It stay exactly in place and seems to loft execeptionally fast when you turn from a side that has compressed it to then expose it to the air. My back never got cold when I rolled over.

    I would rate this bag to allow one to sleep comfortably and soundly through the night at about 30 degrees fully exposed if you have on a pair long underwear and normally sleep fairly warm. At the least I believe anyone could use this bag for a summer bag down to at least the mid 30’s. In this sense Montbell fairly temperature rates the bag at 37 degrees.

    Two other things to mention. The bag has this unique feature of a drawstring on the last panel of baffles at the foot. One could close the last 8 inches of the bag off with a cinch of this drawstring or creat a more confining foot box with it. Don’t know why one would do this unless you were loaning your long to someone short or you were shorter than the regular size and needed to close off even more space in the bag. I choose to remove it and save a fraction of an oz. The other thing I wanted to mention is that the drawstrings for the hood are not differentiated and old school. For a company into making very ligh stuff and inventing fabrics to use in their stuff, they sure use really fat heavy drawstrings. Look more like boot shoe laces. I am thinking of asking my wife who is a seamtress to replace these with lightweight flat differentiated strings. They do adjust the hood and the neck of the bag reasonably well and the hood is very nicely and softly designed to really create a muff around my face. Even when I have not drawn the hood at all it cradles my head and face without constrictions.

    Would I recommend this bag. Unreservedly. Are there nitpicks. absolutely — the zippers and draft tube stifferners in particular.

    Recommendations: Lose the old school drawstrings. Better DWR. Redesign the Velcro top closure. Better Draft Tube Stiffener and anti-snag design. Locking zippers.

    Final thoughts: The only thing that really bugs me is zipping it up and getting the fabric caught. I love sleeping throught the whole night without any cold spots or losing warmth or feeling constricted.

    JUst got back from an overnight at Cooper Canyon Trail Camp in the San Gabriels. Crystal Clear night, very dry (lot of static electricity), 6,250 feet elevation. Started the night at about 50 degrees at 10pm. Decided to sleep on top of a picnic bench and watch the satellites and stars. Slept on my BA insulated air core (love this thing). No sooner did I settle down than a strong Santa Ana picked up and the temp dropped to 30 by about 1pm. The wind convection really robs a bag of its warmth. I began to feel a bit cool in the bag so I donned my Montbell UL down inner jacket and UL down pants on top of my silk long underwear. By 4am the temp had dropped to 25 with the breeze still fairly stiff. Although I slept warm and comfortable, I could feel that the bag was losing warmth because the inner surface of the bag was cool to the touch. I would judge that the wind chill factor was about 20 degrees maybe a bit colder. I feel that if I had slept in my tent, I probably could have gotten away with just the long underwear, but who knows. Even though I had to don the down undies over my long undies, this bag still performed admirably given the chilling effect of the wind out in the open.

    paul johnson


    Locale: LazyBoy in my Den - miss the forest


    good review. well written.

    thanks for sharing your experiences. i, for one, appreciate them.


    Victor Karpenko
    BPL Member


    Locale: Northern California

    Great review. I have the Super Stretch Down Hugger #5 which weights in at about one pound. I too have found it to be very comfortable and warm. The stretch feather is wonderful and not the least bit confining. I think I could be comfortable down into the low 30’s. I have an older version that doesn’t have a zipper. Not a great inconvenience.

    Dondo .
    BPL Member


    Locale: Colorado Rockies

    Thanks for the thorough review, Mitchell. I just got back from a three-day trip in Colorado’s Lost Creek Wilderness where I used Montbell’s synthetic version, the Super Stretch Burrow Bag #4 for the first time. I also have a tendency to roll around when I sleep and am somewhat claustrophobic, so this bag fit the bill perfectly. Last night around 11,000′, the temperature got into the thirtys, I believe, and I stayed warm and comfortable.

    Jeff Black



    Great review!!!!! I’m seriously consider getting the same bag to replace a Big Agnes Lost Ranger 15 degree bag. My main goal is to cut down on weight and compressed size. Thoughts?


    Mitchell Keil


    Locale: Deep in the OC

    Don’t look for this to replace a 15 degree bag. You will be a very cold popcicle if you do. I would consider this a 3 season bag for a warm sleeper. If you are willing to wear warm stuff inside it, one can stay warm to about 20-25 degrees in a tent.
    If you are looking to replace the BG bag with a comparably rated one and you are still looking at Montbell, look at the #2 or #3 super streach bags. THey have the same fit, finish and light weight approach but are nearer to the rating you are looking for. I know someone who owns the #2 and he says it’s like an oven in the 20’s and comfy in the teens.

    The #4 is a bag you would use mostly in the Sierras in the summer. Warm enough for anything you are likely to encounter even at 10k feet.

    Jeff Black


    I should have specified that I’m not looking for a bag that is quite so warm as 15 degrees. For the most part I’m a 3-season warm sleeper and really don’t need to extra warmth. But I’m wavering between the #4 and the #3 and considering the 4 oz difference, but I think that 4 oz. for 5 degrees could come in handy sometime. Now I just have to see if someone here in Portland, OR carries them.

    Thanks again.

    paul johnson


    Locale: LazyBoy in my Den - miss the forest

    Jeff, I have some Montbell SSDownHugger and BurrowBag (synth.) bags. Before buying them, I called Montbell and spoke with Nels at Montbell. He encouraged me to use the upper temp. range number, not the lower number, and pick my bag accordingly.

    Prior to purchasing, in Excel, I worked up a matrix of sleeping bags; two matrices actually: one for down and one for synthetics. Considered a large number of bags from different manufacturers (mostly from WM, MtnHW, TNF, Marmot, Montbell) in order to try to “see” a trend in amount of insulation used. Down was cp. to down, and synths cp. to synths. I noted that for similarly rated bags, my “numbers” (explained below) were ~2.0-2.5 times as great for synth as cp. to down for similarly rated bags – interesting – reveals something about insulating ability relative to weight of the insulation.

    Differences in quality of insulation for down and synthetics was ignored as insufficient info was available to me. Montbell bags use a european rating system to determine FP (fill power) and this is supposedly more conservative than the US method. In fact, I read a while back on a British website that what US Mfr’s are calling, 800, 850, 900 FP was called 750 a few years back, and that special fluffing methods are used to try to boost FP to 850+ and 900 FP numbers. This fluffing is supposedly lost as soon as the down is sewn into a bag. Anyways, that’s another story.

    What I did was compared loft per inch of bag length and normalized for shoulder girth if there was a drastic difference, producing to three decimal digits a number for normalized fill per inch. In the case of Montbell bags, I used the mid-range value between stretched and unstretched which is comparable to WM and FF moderate to snug bags. I needed to contrive this method, since the number of inches of loft is, for some manufacturers, a carefully guarded secret, like they have something to hide. Montbell doesn’t publish and wouldn’t provide me those numbers when I called them. Did they have something to hide? Wasn’t sure. Now I believe, from comparing their “numbers”, and using their bags in the field, that they do not have anything to hide.

    I admit that I made several assumptions here. However, certain bags were easily identifiable as being so light on insulation (some down and some synths) that there was no way that bag could be as warm as other similarly rated bags from other manufacturers. I also only considered higher fill power down bags (725 or greater); not 550FP or 650FP bags.

    As a “standard” so to speak, I somewhat arbitrarily, selected WM bags as the standard to which other down bags would be compared. WM gives inches of loft for their bags as does MtnHW. Sometimes, dealers insist on printing inches of loft for bags that manufacturer’s don’t normally give this info on the manufacturer’s website. Don’t know if these dealer “inches of loft” figures are supplied by the manufacturer or measured by the dealer. I was also comfortable choosing WM as a standard since I’ve owned and used a WM Highlite – short bag for nearly two yrs now. I know that the WM Highlite performs as advertised and was glad to see WM adjust the temp rating down from 40deg F to 35deg F on their website. I’m a cold sleeper and without donning insulated pullover & pants, 35deg F is a proper rating for me with base & mid layers on (only add a pair of 30yr old, 1oz per pair, down sleep socks and a PossumDown beanie for 35deg sleeping).

    Montbell bags compared rather favorably in terms of warmth “numbers”. However, that said, the Montbell bags that I was interested in were typically ~4oz, or so, heavier than a competing WM bag – if a Montbell “SuperStretch” bag’s weight was used, the Montbell Alpine (only internal stretch to hold the insulation against the body; no external stretch to increase girth) bags are generally 2oz less in weight than the similarly rated Montbell SuperStretch bags. Using these “normalized fill per inch” numbers, I found that the Montbell bags were somewhat similar to the competing WM bags and the bag was probably good for a comfortable temp range that was several degrees lower than the upper temp limit range Montbell gives.

    Once I knew how Montbell’s “numbers” compared to WM’s “numbers”, I then assumed that Montbell’s synth. bags performed similar to their down bags in terms of warmth, since Montbell uses the same testing method to determine all of their bag’s ratings. This now gave me a basis for comparing other synth bags (assuming again that diffs in the most modern synth. insulations, while present, were a relatively minor factor).

    I don’t have my XL workbook w/me now, it’s on my other laptop, and so can’t give concrete examples at this time.

    Since then, I’ve found that the Montbell bags perform in the field roughly as I’ve anticipated. I really like the SuperStretch system. I find 59″-62″ of shoulder girth rather restrictive if I’m trying to zip ‘er up, or zip ‘er down to get out and the extra 10″ of expandable shoulder girth that the Montbell SuperStretch system offers makes zipping up and down much easier. I don’t move much when I sleep, so I can’t comment on how useful the SuperStretch is for someone who tosses and turns alot in their sleep. I’ve only got a 40″ chest & don’t know what my max. shoulder/chest girth is, but the 59″ of my WM Highlite is a snug fit – quite snug, but usable. I have to go through contortions to zip it up and down; not so with the Montbell SuperStretch bags (not the Alpine versions, they’d have the same issues as the snug WM bags).

    I hope that this info helps you some in selecting the right Montbell bag. If you feel that the SuperStretch is unecessary then, go for the Alpine bags and save 2oz in wt over the comparable SuperStretch. Montbell only offers the Alpine versions in selected bags (every other “numbered” bag – i.e. most of the odd numbered bags, viz. 1, 3, and 5 if memory serves).

    Curt Peterson
    BPL Member


    Locale: Pacific Northwest

    Great reviews! Nice to see real world experiences with the SS bags…

    I’m curious how well the bags insulate when fully stretched out. I’m in the XXL crowd, and the bags that fit me well are all in the 69-70″ girth range. Not many light options in that category. Like the original reviewer, I also sleep on my side and toss and turn a lot. I’ve thought about the SS bags for awhile as a solution, but can’t find them locally to actually check out.

    So, would they work for a “big guy” in your opinions? If they’re stretched out almost to their max routinely, will they still insulate well as the down ‘spreads’?

    Any insight on this would be appreciated.

    Thanks again!

    Michael Freyman
    BPL Member


    I too am interested in the functionality at “full stretch”. Maybe one of the average size gents can put on 37 layers of clothing until they get to a 70″ girth and let us know how it works??? Of course, this would probably put you at a -70 temp rating. :)

    Jeff Black


    I’m happy to see that I’m not the only one that uses Excel to do a comparitive analysis. Although you have taken the time to be more thorough than I have.

    Which Montbell bag(s) do you have and what have you discovered the comfortable temp range to be for each one?

    I’m a big guy, which is what led me to the Big Agnes. I really do like the bag I have now, Lost Ranger Long 15 degree, because of the extra room which got me looking at the Montbell Superstretch line. Originally I was simply looking for a lightweight bag to add to the BA that wasn’t quite so warm, but now I’m considering a Montbell bag to fit both spots – warm and light.

    I’ve never seen myself as the type to need more than 1 sleeping bag, but maybe I’m almost there. I would have said the same thing about backpacks, but now I have 4 of them.

    What really got me started was when I was seeing long bags from various mfg that weigh 1.5 lbs. compared to my current 3 lb bag. The thought of shaving off 1.5 lbs is very attractive. Plus I just got a REI UL 45 in hopes of using it on 1-3 night trips and the lighter bags would take up much less room.

    I was very close to getting the Big Agnes Yampa 40 degree bag. The long weighs 1 lb. 13 oz. at which point I started thinking why get a 40 degree bag when I can get a much warmer bag that weighs even less. Now you can see my thought process and what got me to where I am today. I’m in no rush so I’ve got plenty of time to think about my options.

    I’d also considered a Valandre Mirage +20 bag, but am not convinced that it would be wide enough. Not sure if anybody out there has ever used one or not. Anybody?

    Ok, enough of my yammering. I just joined BPL a few days ago and am very much enjoying it.

    Thanks, Jeff

    paul johnson


    Locale: LazyBoy in my Den - miss the forest

    Curt and Michael, I’m at the other end of the spectrum, i.e. suit size 40 extra-short (40=chest;not waist) and I don’t toss and turn – fixed back sleeper. So, take my opinion with a grain of salt. There’s up to 70.9″ of expandable outer girth, and related compressed inner girth, in the Montbell SuperStretch bags when fully s-t-r-e-t-c-h-e-d to the max. When stretched this far, the lighter weight/warmer temp bags get pretty thin. Since this not the normal sleeping girth for me, I can’t really tell you at what temp this max. stretched bag would work down to. I suspect that it would not even reach down to the upper temp range number (maybe 5-10 deg warmer than that upper temp range number), but this is just a guess on my part since I’ve never tested it in this fashion, nor am I able to personally do so. Sorry, I can’t be more help. If I were forced to make a suggestion, I’d say, if your girth is closer to 70″ pick a bag with an upper temp range rating that is 5 to 10 deg F lower than what you want for a minimum comfortable sleep temperature. Using this “guess” as a guideline I’m not sure how that compares to other Mfr bags in terms of a bag’s weight. As someone else said, the lightest of the UL bags are all too tight for someone with a large girth. I’m guessing that semi-rectangular/semi-mummy bags are the ticket, or a full rectangular bag with a separate down hood, like one from FF (Feathered Friends or Nunatak, or make a Ray-Way Bomber hat). Of course, bags with this shape are heavier due to their shape and additional insualtion required.

    J R


    I use a synthetic Montbell #4, and wouldnt advise using it if your going to have to max out the stretch.

    It isnt intended to “stretch to fit” (though it can”, it is intended to “compress to fit” to reduce area that needs heated, an to keep the area close regardless of how you toss and turn.

    If you like how the stretch baffles work, but want a larger cut bag, you might be able to find a Sierra Designs “Flex Series” bag on closeout. It uses the same elastic baffle technology.

    Campmor has the SD Van Winkle 15Deg bag for sale at $160. Weight is about 3lbs. About 1lbs more than a compairable MontBell, but it has the “nightcap” hood which covers the bulk of the weight, and is oh so nice if you toss and turn. It also uses 600down rather than the 725 of the MontBell, so its got a higher fill weight, and theres the rest of the pound.

    More inline with compairing the #4, SD’s REM is at Campmor for $130. Rated to 35Deg. Again, heavier due to the hood, 600fill down, and being cut larger to fit the American frame.

    paul johnson


    Locale: LazyBoy in my Den - miss the forest


    Preliminary Info to put the specifics in context.:
    I have several bags, both down and synthetic, but no winter bags yet, only, what I would call, spring&fall bags, and summer-only bags. I’ve duplicated synth. & down bags, depending upon use in rainy conditions for more than shorter 3-day excursions (though I rarely take these, but am always planning to). I’ll admit that this is perhaps a bit naive, but I don’t have the extensive long trek or Thru-Hike experience of many of the Forums more experienced participants. I just don’t like to take chances, especially when it comes to my “sack” time and a warm, dry, comfortable night’s sleep. So, I err on the side of caution and safety. You may not want to follow my extreme example in this – one ends up with a lot of bags.

    I don’t plan to use a synth bag for winter weather due to its weight and volume. I do own a 20deg MtnHW Trekker – short bag, bought some time ago. I recently had it out in overnight lows of 16-18degF, also wearing Thermawrap pants and a Cocoon pullover. While not cold, I wasn’t warm either. I believe the Trekker is good to colder temps than the BurrowBag#3, IMHO. This is based upon the “numbers” in my XL spreadsheet since I don’t own the BB#3.

    I consider myself a cold sleeper. For colder weather 25-45 deg F, I typically don lightweight down sleep sox and a wool beanie (cf. my prev. post for more specifics on these two items). To extend the temp of any bag I own, I can don Thermawrap pants, and a BMW Cocoon pullover for colder spring/fall (and colder winter) temps, or long johns and PossumDown Vest or Sweater for warmer spring/fall temps. I don’t plan to wear my added insulation to sleep, preferring to keep it as an extra safety/comfort margin should the temps plummet unexpectedly that night. About the only time I get sick is if I get chilled, so I want to be able to avoid this if possible. This approach of mine is not in keeping with the UL philosophy as I don’t plan to wear my insulating layers to sleep if the expected overnight low temp is encountered. I save them for the unexpected.

    Now to answer your specific question:
    The following info is only based upon my limited experience, YMMV.

    SSDH#3 = 30 deg F
    SSDH#5 = 40 deg F

    [The above temps don’t include donning insulating garments other than the beanie and down sox.]

    [For the below temps, nothing extra, beyond normal daytime base and mid layers, is donned – not even beanie or down socks.]

    SSDH#7 and SSBB#7 = 50 deg F

    BurrowBag UL = 55 deg F. [My first Montbell bag. This one does not see much use anymore, having been replaced by the SSBB#7.]

    UL DownHugger – don’t know yet, recently purchased and haven’t used it yet. I’m guessing 55 deg F with a beanie (no hood on the bag). Based upon other hoodless experience, I plan to wear a hat or beanie to sleep at 55degF since there is no hood.

    I don’t own a SSBB#5 but expect it to perform similar to the SSDH#5. Not sure if I will purchase one.

    I intend to purchase for next winter either a SSDH#2 or a SSDH#1 (I expect/hope them to be 20degF and 10degF bags, respectively with only beanie and down socks added to base and mid layers).

    Hope this info helps.

    Jeff Black


    I bit the bullet and went to Next Adventure in Portland, OR and picked up the Montbell UL Super Hugger #3. Now I just have to schedule a backpacking trip for March so I can give it a try. And by then I may decide to buy the Tarptent Rainbow as well. Hey, you only live once – might as well enjoy it.


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