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Ultralight and ultra lofty.

The Western Mountaineering UltraLite Sleeping Bag lives up to its name by keeping your load manageable while still packing in a hefty dose of premium 850-fill down for those chilly nights. A soft taffeta lining caresses trail-weary skin and, thanks to the Pertex shell's breathability, the climate inside of the bag stays comfortable on balmier nights.

  • Highly breathable, water-resistant Pertex shell protects the down insulation from frost, condensation, and spindrift
  • Packs 16 ounces of ultra-premium, 850-fill down insulation to retain your body’s warmth and maintain a super-high warmth-to-weight ratio
  • Interlocking draft tubes and a down-filled collar prevent energy-sucking drafts from zapping your slumber
  • Slightly narrower shoulder girth helps eliminate pockets of dead air for improved warmth retention
  • Western Mountaineering bags are made in the USA

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Western Mountaineering UltraLite Sleeping Bag: 20 Degree Down

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Here's what others have to say...

The degree is 20F. What does that mean? Feedback much appreciated!

Responded on


The 20F temp rating means that Western Mountaineering has built this bag to perform down to that temperature.

Shoot me an email anytime you have questions!

Jared D.
Expert Gearhead

Why do you not show normal metric weights and measures. They would be a help for anyone outside America as that is the only place using old measures these days. The vast majority of UL hikers are metric familiar as "gram counters".

5 5

High Quality, Lightweight but lofty

  • Familiarity: I've used it once or twice and have initial impressions

I agonized over the Ultralite and Alpinlite sleeping bags. I am a side sleeper and initially went for the Alpinlite. I tried it out, and this bag is perfect for bigger people. I am 6'1" and 175 lbs. This bag is too big for me. It packs into a small stuff sack, but not small enough for me. I returned it and went for the Ultralite. This bag is just as "thick" feeling (quality), fits me side sleeping and packs much smaller than the Alpinlite. I ordered a sea to summit 10 L bag to compress it even further.

Trying to decide between this or the WM Alpinelite 20 degree bag. Can't really tell what's different. Looking for something that's 3 season, light/ultralight and good for back AND side sleeping as I sometimes roll around. Is the only difference that the Alpinelite is a little roomier? Feedback much appreciated!

Best Answer Responded on

Hey Cri,

You nailed it! The two bags are pretty much identical except that the Alpinelite is a roomier cut.

Feel free to hit me up with any questions or if you'd like to place an order.


Unanswered Question

which outer material is used on this bag? on web page it says Extremelite but i can not get any info how water resistant is this fabric. How does it compare to Pertex Endurance? Can you tell me how much g/sm? Thx

Does "right zip" mean the zipper is on my right hand side as I'm laying in the bag?

Responded on

Hey Robert, Leta here with Western Mountaineering. It does eaxctly. Some people don't care which way, but if you are right handed, it's a bit easier to zip up and down when the zipper is on your left side, as you reach across your body.

Hope this was helpful!


Unanswered Question

Can someone please post a picture of this bag compressed next to a Nalgene for comparison?

Will a 6' left zip together with a 5' 6"...

Will a 6' left zip together with a 5' 6" right? If so how does that work? Are the zippers actually the same length and only the tail of the one bag longer? Thanks

Responded on

My wife and I try that same setup, but with a regular right and a long left zip configuration. The bags mate well (assuming similar zipper size and type), but there's a large gap between our shoulders where her zipper ends and my bag extends a few extra inches. This creates a bad draft, and cold spots. The foot of my bag also reaches a little farther than hers, which is expected. The positive side is that it gives both of you a little more room to move around, and keeps the bags in place if you turn in your sleep. It isn't advisable on nights getting down to the bag's rating though, because of the mismatch.

4 5

awesome bag

  • Familiarity: I've used it several times

Really great sleeping bag; lightweight and warm for the rating.

Can't decide on the ultralight or the...

Can't decide on the ultralight or the alpinlight. I am skinny - 6-2 150 pounds and am worried the girth of the alpinlight might be too much. However the extra room may be nice for layering and room to move around. Any suggestions?

Responded on

Your worry is well founded. If the bag is too big you will have dead space that needs to be warmed. On the other hand, if you feel like you prefer to layer and have room to move around and can live with the extra space, the the Alpinlite might be a good way to go. Best of luck!

Responded on

I am in the same boat. I am just under 6 feet tall and my current bag claims to be 62 in shoulder circumference and I am worried about the ultralite bag being to tight.

5 5

Excellent & light weight

  • Gender: Male
  • Familiarity: I've put it through the wringer

Really warm for a bag that packs down so small. Weighs almost nothing, but is warm enough for late fall/early winter. Comfy down to -10 C if you wear a wool shirt :-)

5 5

Amazing Bag- Bag For Life

  • Gender: Male
  • Familiarity: I've used it several times

I first bought the HighLite 35 degree bag, slept out in New York in November and was a bit cold, so I returned it and got the UltraLite. The bag is incredible- super warm, great construction, packs down very small. Expensive, but I expect it will last for decades.

5 5

Like it but may be too small

  • Gender: Male
  • Familiarity: I've used it once or twice and have initial impressions

I bought the Ultralite and the Alpinlite to see which fit me better. Both bags are very well made and both are the long (6'6") size. The stitching is perfect, the zippers work great without snagging although I am careful with them just to be safe. The problem for me is determining which one to keep. I think this is a fairly common occurrence, so I thought I?d try to provide some information for anyone trying to make the decision.

I think I've read every article on the internet about both bags and am really sold on staying with WM. I'm 6'1.5" and fluctuate between 170 and 180 lbs. My chest measurement is 42.

It seems like the Ultralite's shoulders are fine at 60"but the hip measurement feels fairly tight. I think the foot measurement is fine, although I can notice the inch difference on the Alpinlite in that area.
As far as the Alpinelite...I really like the foot measurement of 39". I also like the hip measurement of 56" a lot more that the Ultralite's 52". It doesn't seem like a lot, but it is to me. I'm mostly a side sleeper in case you were wondering. The Alpinlite?s should measurement is what makes me wonder which one to keep. It?s really large at 65?. There is considerable difference between the two and it?s almost as if I need the Alpinlite?s hip and foot measurements with the Ultralite?s shoulder measurements. The bags are so similar with respect to function, that it doesn?t make sense to keep both. I may end up keeping the Alpinlite because I flop around a lot at night. The perfect WM bag for me would be a 20 degree bag with the following measurements ? 60-62?shoulder, 56? hip, 39? foot.
I give the bag 5 starts because the fit and finish is immaculate and everything works as it should.
One more note - If you are over 6 feet tall go ahead and get the long. It will be perfect once you extend your toes.

Responded on

Thank you for your review. I am in the situation and have been struggling between these two bags. I ultimately want the Alpinlite but it is not in stock at the tim of this response and I need it before the beginning of Sep ;(

I am 5'7 could i fit into the 5'6 bag or...

I am 5'7 could i fit into the 5'6 bag or should i just go with a 6 and put some clothing at the bottom to fill in the gap?

Best Answer Responded on

Go with the 6'. If you are too big for a bag, you will over-compress the insulation and lower the temp rating.

I'm a petite female looking for my first...

I'm a petite female looking for my first down bag after borrowing a friends' and loving it.
I swore I'd never camp again with temps under 25 degrees with my current bag.... would the ultralight be warm in temps down to 15? What temp bag should I actually be looking for? These temp ratings can be confusing!
I'm like a lot of women...cold feet, hands, cold everything....
I'm also interested in a bag that packs light and small..this thing goes with me on my bike, suitcase, and whatever couch I might be crashing on....
Thanks for any advice!

Responded on

If you cold take the warmes sleepingbag you can take.
The EN rating is what you lokking for. it said women r cold and need a warmer bags...dont go by the US raiting, you get cold
I hope it's help (:

Best Answer Responded on

Disregard what Guy said--EN ratings are good for comparing different brands of bags but don't give you an accurate temperature that you'll be comfortable in.

Western bags are over filled and conservatively rated. I have slept in a 25degree Western sleeping bag in 25degree weather and I was perfectly warm and I get cold easily. The key is the amount of down put into the bag. Not only does Western use the highest quality European goose down they can get, they then put large amounts of it in the bags.

I'd trust the temperature rating with Western Mountaineering bags. The average person would be warm 5 degree below the rating, but if you are thinking you'll regularly experience below 20 degrees AND you run cold, I'd think about the Versalite for a couple ounces more. You could also get a sleeping bag liner that would boost the temp rating on the trips you think temps would be colder than 20.

Hope this helps...

Responded on

As far as EN ratings go- I have never, ever found any sleeping bags that have met of exceeded WM's in accuracy. WM has never let me down and cost me a single night's sleep because I was cold....the only problem is not wanting to get up in the morning.

Responded on

Western mountaineering bags are indeed conservatively rated. If you look at a UK site, you'll get the EN ratings (EN is required in europe I believe). Over in the EU the Ultralite is billed as a 16F bag rather than a 20F as in the States. I think they refrain from quoting the EN rating because they have built a decades long brand on their old conservative ratings and want to maintain reliability from year to year over marketing hype (even if it is in their favor).

Why is there no Left Zip option for the...

Why is there no Left Zip option for the 6ft bag?

Responded on

When Backcountry runs out of a certain item, it disappears from the purchase options. Left zip is available, but Backcountry doesn't have any right now.

im looking for a bag to use on my thru-hike...

im looking for a bag to use on my thru-hike next year on the PCT, and its a toss up between this and the apache. is the couple ounces of weight worth sacrificing the durability of a regular WM bag?

Responded on

Having used Pertex in both bags and jackets for a while now, I can tell you that durability shouldn't be a concern. Unless you intentionally pull your bag through thorny bushes or slide down abrasive rocks using the bag as a sled, you'll be fine.

Between the two bags, I'd be more concerned about fill weight. You get an extra 3oz of down in the Apache. That could make a huge difference on the PCT. If you decide to go with the UltraLite, call WM and ask them about having it overstuffed. Then, you can get the benefits of more down and keep the light weight.

5 5

Took the big leap

I've spent my career working in large wilderness areas in MT and WY. I've have NEVER been a fan of down gear and 99.9% of cold weather gear I own is synthetic insulation. Believe me, I've been spanked by Pa nature far too many times in the backcountry to take the lessons learned lightly. However, my main backpacking, ski, and inflatable kayaking buddy has owned one of these WM bags for YEARS of constant use. I on the other hand have gotten by very well on NOLS garage sale MH used synthetic bags and a MH lamina(?) -40 bag for winter. (as an aside, I will NEVER own another synthetic bag made by the furry rodent people, not good). I still have my 1969 Outward Bound REI McKinley down bag that has outlived it's usefulness (lack of ventilation and loft, i.e. cold spots). However, since my retirement goals in 20 months are to start ticking the long distance trails, I've been retooling my gear for as light weight and quality. Knowing how pleased Curt has been and researching the rep on these bags finally caused me to reluctantly shell out the big buck...(on sale). I am extremely pleased with this top quality made purchase. So far so good, and am confident in the long run that it will perform as well as it has for Curt and the other reviewers have raved.