Western Mountaineering Alpinlite 20 Degree Sleeping Bag

I absolutely love this bag and would have kept it if I was bigger. I was initially torn between the Ultralite and Alpinlite, and ended up with getting the Alpinlite first. After some time in that bag I just found there to be too much dead air from the extra girth, but the Ultralite was snug to the point where I was worried about down compression if I had layers on. I returned the Alpinlite for the Versalite since it fit more snugly and rolled with me when I slept.
While the Versalite is slightly warmer than the Alpinlite or Ultralite bags, the chest girth sizing falls between the Alpinlite and Ultralite, which was perfect for me. The full length zipper allow for easy venting and I have no worries of overheating—I generally sleep very warm. The Versalite also comes with one more ounce of down than the Alpinlite, but is slightly narrower and thus warmer overall and spans a wider degree range. The full length zipper also allows the bag to be opened up and used like a quilt in warmer weather. I have taken both bags down to low 20s and the high teens and slept comfortably in a baselayer with the neck baffle completely loosened in the Versalite. The Alpinlite required me to cinch down both to trap in heat to fill the dead space.
The materials are top notch, the down is super lofty—WM bags are great.

6'5", 235lbs. Wear a 50L jacket, 34-36 inseam and waist. My arms aren't huge but they won't fit into the "check your blood pressure" thing at Walgreens. Point is, I take up some space.
The Alpinlite was perfect for my size. I move around a bit and never once felt claustrophobic, but I can't imagine having less space. I think I would have been freaking out in Ultralite. The 6'6" version of this bag couldn't have been a better fit. I never got cold at altitude and only got hot once at lower levels, but it was around 50* and I was still wearing a shirt and shorts so that one was on me. All it took was unzipping the bag a bit and it regulated nicely.
I thought I was crazy dropping almost $500 on a bag but this thing is absolutely awesome and it shows in the details: the stuff sack is perfectly sized and the zipper has smart things like a stiff backing so that you don't catch the bag in the zipper. I can't say enough great things about this bag.

This bag has every right to be big, bulky and heavy...but it's not! This is the bag that I use the most. 20 degrees keeps me comfortable 3 seasons in the mountains and during spring and fall in the desert. I've never found a 20 degree bag that lofts as tall as this one. It's roomy for my stout stature yet weighs a scant 2 lbs. The stuff size is slightly greater than a football. Although this is made from Western's least water resistant shell, I awoke in the Cirque of the Towers one morning in Sept. to 24 degrees and 4 inches of snow covering me in my Alpinlite. (The stars were out when I went to bed. Why would I pitch the tent!)The bag was dry. I was warm. Just rolled over and went back to sleep.
If you're an ultralite fanatic and want to save another 1/2 lb., get the Ultralite. While you're wrapped tight in your 1 lb. 8 oz. bag, I'll be makin' babies in mine.

For starters, I'm a bigger guy, wide shoulders, overweight, the whole package, so usually I find mummy bags pretty claustrophobic, but the AlpinLite fits pretty well, it's not so tight that I can't move, but it's not so cavernous that it looses its function as a mummy bag.
I took this bag with me to the Grand Canyon in Nov '09, and while the night time temps dropped pretty low, down into the 40s or 30s, I was so toasty I had to open the bag up a little until fairly early in the morning. The weather was nice so I just set up on a picnic table and slept under the stars, no issues with condensation or anything.
I'm looking to do some winter camping next, I think due to the continuous baffles, I can probably shove some of the down from the bottom around to the top and maybe get a little extra loft, so we'll see how that goes.

Only used it twice but I love the fit. I'm 5'-2" and the bag fits perfectly with some room to spare for extra layers at the bottom.
My first trial was at the base of Mt Washington and the outside temp had dropped into the low 30s. I was cold with my base layers on but I run cold.
The second trial was in VT and the outside temp was in the 50s and damp. I was a bit too warm in the base layers on but boxers & undershirt was just right.
The only downside I experienced with the bag is the smell it gives off in damp conditions. The down smell can be a bit much even if the bag isn't directly wet.
Overall love the bag!

I have been running the Alpinlite for a few years now. I really like the warmth and lack of weight.
The width is a bonus for me, as I am rather broad across the chest(44 coat size)and am a side sleeper.
I haven't had this bag much below 15*F, but in those cases it was still very warm-I have a hunch I could go into the high single digits with just a base layer and wool cap sleeping in the Alpinlite.
I will never part with this sleeping bag.

i've been hiking 2 to 3 times a yr for the last 20+ yrs and i have finally found the bag i'll use for the next 20. this is probably the 8th bag i've owned ( 1st down ). I.m 6'1" and 215 lbs and i never feel restricted in this bag. i used it down to 30 deg with just a light base layer on. no cold spots. great workmanship ( made in usa ). just buy it !!!!!

Used for the first time. Very light-weight and obviously very high quality bag. Unfortunately the temperature was between 50-60f degrees and I was too hot. I finally got comfortable around 4 am with the bag unzipped all the way. I think when I get to higher altitude, or the temp drops to around 30-40f it will be perfect.

This is a premium bag. It's a mummy bag, but it's wider than a traditional mummy... which is great for those of us that like to move around while sleeping. It's very warm however, and has some cool features. It has excellent loft and compresses nicely. I have a full video review at backpackersreview.com

Finally a warm and light sleeping bag for big guys that doesn't fit like a condom. Field tested it this autumn in the Dolomites in Italy in open air around freezing temperatures. Didn't need long underwear to keep comfie. Great product, fully worth the price.