Rating: 4 / 5
I am 6 foot 3 inches, weigh 175 age 57 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 3 months ago and have used it 6x.
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. I now just slide in and out of the bag without using the zipper). 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 in mid June 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 create 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