Free 2-Day Shipping on Orders Over $50* – Limited Time Only

Detail Images

  • Western Mountaineering UltraLite Sleeping Bag: 20 Degree Down One Color

Available colors

  • Western Mountaineering UltraLite Sleeping Bag: 20 Degree Down One Color

Western Mountaineering UltraLite Sleeping Bag: 20 Degree Down

$484.95 - $514.95

Free 2-Day shipping on orders over $50*

Select a Size:

Select options
  • Select options
    • 5ft 6in/Left Zip
    • 6ft/Left Zip
    • 6ft/Right Zip
    • 6ft 6in/Left Zip
    • 6ft 6in/Right Zip

    Select a Color:

    Select options
    • One Color
    5.0 5 22

    22 Reviews


    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 ExtremeLite shell's breathability, the climate inside of the bag stays comfortable on balmier nights.

    • Breathable, ultra-light, packable, and high-thread-count ExtremeLite shell fabric encases the insulation without adding unnecessary weight
    • 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
    • Item #WES0031

    Tech Specs

    [shell] ExtremeLite, [lining] nylon taffeta
    850+ fill down
    Max User Height
    (short) 5 ft 6 in, (regular) 6 ft, (long) 6 ft 6 in
    Shoulder Circumference
    (short) 59 in, (regular) 59 in, (long) 60 in
    Hip Circumference
    (short) 51 in, (regular) 51 in, (long) 52 in
    Foot Circumference
    (short) 38 in, (regular) 38 in, (long) 38 in
    Fill Weight
    16 oz
    20 F
    Storage Sack
    Stuff Sack
    Stuff Size
    7 x 13 in
    Claimed Weight
    (short) 1 lb 12 oz, (regular) 1 lb 13 oz, (long) 1 lb 15 oz
    Recommended Use
    ultralight backpacking, camping
    Manufacturer Warranty

    Tech Specs

    • Reviews
    • Q & A

    What do you think about this product?

    Have questions about this product?

    Best bag I've ever had and great service

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

    The first bag I purchased was stolen off my front porch, and Backcountry sent me a new bag and the sea to summit comfort plus pad that was with it immediately, no problem! They were incredibly understanding, it was a huge relief. I took it on a weeklong trip to Costa Rica and it performed fantasticly with nights dropping just below 40 degrees and I woke up cozy, maybe a little sweaty (my fault for not regulating the zipper opening) with no interruption, other than monkeys howling. I aired the bag out on my hammock every morning for about 10 min and there was no funny stink to air out when I got home :) great bag so far!

    Amazing Sleeping Bag

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

    I took this bag for the first time after i bought it on a 22 mile snowshoe up in the BC mountains. We ended up making a quinzee (snow shelter) for 6 people. I used this bag with a neo air xlite mattress beneath me and a wore a down jacket inside. Temps got down to about 14 degrees (-10 c), past the limit of the bag which is 20 degrees. Even with some condensation from the shelter accumulating on the bag i didn't feel cold. It wasn't toasty warm but it was comfortable. I was able to sleep through the night no problem. I am 5'7", 185 lbs with wide shoulders (44") and a side sleeper. This bag doesn't have a ton of room inside but it was big enough for me.

    3 years with the ultralight

    • Familiarity: I've put it through the wringer

    I've had this bag for years now camping across Washington St, Oregon, Montana and Cali. I've used it for summer and winter conditions and couldn't complain one bit. below 30 degrees you can feel the cold if the winds kick up but its true to its 20 degree limit. It's also stood the test of time and kept its warmth over the years.

    Light and Fluffy

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

    The first thing I noticed when I got this bag is it was incredibly light compared to my old one. I have not gotten a chance to use it as of yet, but will update once I do.

    Update: Got to take it out over the weekend to Capital Reef, temps got down to mid 30's or so, and it was phenomenal compared to my old bag that has lost all its loft. This thing is so warm and comfortable, and I didn't find it constricting at all. Very happy with my purchase.

    This Bag is WARM

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

    I'll start by saying I run very very cold. I was using a 3.7 lb. zero deg bag year round (except for hot desert camping) for the last 7 yrs and I have no problem sacrificing weight for comfort. I was concerned with the continuous baffles on this bag and losing the heat underneath me since I toss and turn a lot but as it turned out it was never an issue. I did a 5 night 6 day Sierra trip at the beginning of August (warm for some, cold for me) and would normally take the zero but I was on a mission to drop weight so after reading the incredible reviews I bit the bullet and spent some money on this bag and it's one of the best purchases I've ever made.
    It's so light, it definitely helped me get to my goal pack weight and it packs so small it's hard to believe how warm it kept me and how well it lofts. I slept with a light base pant and shirt, no socks and when we had a couple of really clear, cool and very windy nights and I got chilled, I tightened the collar a bit and like magic the heat was instantaneous. The pull ties were easy to work with on the hood and around the neck and I was able to find the perfect combo. Another plus is my zero zipper ALWAYS snags, every time, and this one didn't snag once, even from an opposite pull across my back.
    This bag blew me away. Based on the reviews I knew it was a good bag but I didn’t expect it to perform as well as it did for me and I see many years of use in it's future. I would highly recommend it to anyone looking for warmth and to save weight.

    Fantastic bag

    • Familiarity: I've put it through the wringer

    This is an amazing bag. Super warm, super lofty, and super lightweight. You usually don't get all that in a single package. Western Mountaineering makes lifelong bags. I have several of their bags and they're all amazing; this one is no different. I have buddies that have over 20 years with their WM bags. This is a fantastic spring, summer, and early fall bag. It's true to its 20* rating.

    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.

    Amazing Bag- Bag For Life

    • 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.

    Like it but may be too small

    • 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.

    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.

      Light weight and warm

        So far, I have had the bag out for two trips and it has performed very well. The lightness and compact size of the bag help me cut down on pack weight and size. It sleeps very comfortably and I can't wait to get it out in some colder weather.

        Light weight and warm

        Changed the game

          My old bag was a Marmot Sawtooth 15. That bag got great reviews and was warm enough I guess, but it just didn't compare to the WM UltraLite. The Marmot weighed nearly twice as much as this thing. This bag has brought my base weight down to under 8lbs, and I can absolutely notice a difference. I don't even have to use my hip belt on shorter trips, my bag is so light now.

          Other than weight, another great thing about Western Mountaineering is that their temperature ratings seem to be very accurate. I had used my Marmot bag in 20 degree weather before and was uncomfortably chilly in the morning. It got to about 25 where I was this past weekend and I was still extremely toasty, leaving me no doubt that this bag will go to at least its rated temp, if not even lower without problems.

          Not for the money...

            This is a light bag. It is warm (I found the rating to be a little optimistic). My biggest complaint (and why I got rid of mine) was that the material is not nearly down-proof enough: I was always loosing feathers or being poked by feathers. If you want the best US-made, lightweight down bag that doesn't spear you during your slumber, check out Feathered Friends - hand made in Seattle.

            note from Gary at Western Mountaineering: If your bag leaks down through the fabric I would recommend sending it back to us for evaluation. It may be covered under warranty and we may decide to replace it but need to see it first. Some down may migrate through the material occasionally, especially if a compression sack is used, but if there are more than 7 or 8 places where down is poking through the fabric then I recommend contacting us or sending it back for evaluation.

            Can a bag be any better

              Switched over to this bags several years ago an have carried for over 1000 miles. Will not get another bag. Super light weight and very warm and it can be packed smaller than a 32oz water bottle.

              SLEEP IN STYLE...!!!

                I Recently took my Western Mountaineering UltraLite 20 degree bag on an early season AT thru-hike. I combined it with a silk liner and slept comfortablly with tempature droping into the teens. When tempatures dropped into the singles and below zero I had to add my space blanket to the mix. It compressed very nice and quickly regained it loft once out of my pack. The full zipper allowed me to use it as a quilt when tempatures warmed up, and the mummy style allowed me to cinche up and trap body heat when it got cold.

                The Western Mountaineering UltraLite 20 degree is one of the best bags out there...!!!!

                I think a Western Mountaineering Hot Sack is a much better option than the space blanket. But there is a trick to using it. Once inside your body can't self regulate temperature by perspiring. So you may overheat and sweat until wet. The trick is to only be inside of part of the bag when warm, e.g. move it down from your neck to your waist, or to you knees when warm. Then you will still be warm, but won't sweat inside the Hot Sack. I think the Hot Sack is an amazing way to add the ability to do more cold with less weight!

                Would this bag work in summer as well as winter? Also, is it waterproof or would I need a waterproof bag to put it in?

                Hi Sharon, thanks for writing. The Ultralite is awesome! 20 degree is a great temp for most seasons, but the great thing about this bag, and other all other bags from Western Mountaineering that are greater than zero degree in their temperature: It has continuous baffles. What does that mean? Well, you can move the down from the top of the bag to the bottom of the bag by sliding it around to the bottom. This will give you less down on the top for when the temperature is warmer outside and you do not want to over heat. Does this make sense? Very cool design.

                Now, about the ultralite: It is a narrow and efficient bag. "Efficient" in that you are not wasting energy heating up dead space in the bag. BUT... it's too narrow for me. I love the 20 degree option, but for something more roomy and comfortable to move in, please consider the Alpinlite or Terralite from Western Mountaineering. Those are 20 and 25 degrees respectively, and have a bit more room, if you would like this.

                About waterproof, no. Are you sleeping without a tent? If you are out in the elements in this bag, it will get wet. So you need to have a tent or a bivy sack. Most important for us in this bag is your comfort. Your body needs to "breathe" and when you have a waterproof barrier to the bag, not only is it far more expensive, but it is clamier (is that a word?), and hotter. We do make bags in Gore Windstopper, not technically waterproof, but very close to that. Those bags are best for cold wet environments. What is your situation where you will use the bag? Where do you live?

                I hope this was helpful. Please reach out to me in the Backcountry Community if you have any other questions!


                Western Mountaineering Rep

                Anyone have thoughts on AlpinLite vs UltraLite for a 5-6 ~130lbs female, side sleeper? Do girls find the UltraLite too snug because the're not shaped like a carrot?

                Anyone have issues with dampness/wetness with this bag?

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

                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".

                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!

                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?

                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!


                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


                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.

                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?

                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!

                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?

                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!

                Best Answer

                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...

                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?

                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?

                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.

                I have a Marmot Pinnacle, and the regular...

                I have a Marmot Pinnacle, and the regular size is just right for me. Anybody know how comparable the Ultra compares, size-wise?

                Is the ripstop shell on this bag water...

                Is the ripstop shell on this bag water resistant or repellent? And is there any moisture-wicking property to the lining?

                Best Answer

                The "Pertex" shell offers slight water resistance but not enough to rely on more than normal condensation build-up & the inner lining doesn't wick but does breathe. This is from the manufacturer: "These bags are designed for special applications where compressed volume and weight are critical factors. Although some durability is sacrificed with these lighter fabrics, our ExtremeLite™ bags are perfect for the lightweight specialist."

                Time for a new bag, and Western Mountaineering...

                Time for a new bag, and Western Mountaineering is going to be it. The UL would be my first choice, based on weight alone, but I'm concerned about the shoulder circumference. I'm about 21" across, and prefer a roomier bag, and also sleep cold. Would I potentially be better served with the Alpinlite or the Badger MF in both the width and the rating? Also, when WM says that their bags are for experienced gear users, what special considerations might that entail in terms of precautions and care?

                Best Answer

                Hey Phil. The Badger was the first Western bag I purchased. It's spectacular. By Western standards it's heavy but if you stop and think about it, 2.5 lbs. is damned light for a REALLY wide mummy. It's cushe. Having said that, I now use my Alpinlite more for carrying on my back since I sleep warm and it's wide enough. You couldn't go wrong with either bag you're considering. I know. I have both.
                Sleep cold and don't mind that extra 8 oz? Go for the Badger.
                Wanna go lighter without feeling like a crysalis? Avoid the Ultralite and get the Alpinlite.
                Want the warmest, lightest, most packable 20 degree sleeping bag on the planet? The Ultralite is the one. Period. My 200 lbs puts a little too much strain on the girth. That's why I prefer the other two.
                Oh, the experienced user thing...nothing to worry about unless you enjoy scree sledding in your sleeping bag. If that's the case, choose another. Sleeping on the ground has never been a problem in either the Badger or Alpinlite. They're plenty durable. I use them a lot between washings and when I do occasionally wash them, I give 'em an extra rinse cycle in the front loading washer at the Laundromat. Turning the black inside-out and giving them a good dose of sun is the best way to clean them unless they get too manky. It also lofts them brilliantly.

                Phil, if you haven't already purchased, I would highly recommend getting either the Swift or Swallow from Feathered Friends instead of a WM bag. These bags are built with better materials (higher water repellency and increased down-proofness - keep your feathers in the bag where they belong!), I find them warmer than WM bags, custom colors, and also made in the US.