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  • Western Mountaineering - UltraLite Sleeping Bag: 20 Degree Down - Royal Blue

Western Mountaineering UltraLite Sleeping Bag: 20 Degree Down

$485.00 - $515.00

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    • Royal Blue

    33 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?

    USA made!

    • Familiarity: I've used it several times

    I love these Bags. They have never given me problems with warmth, they compress down nice and compact and are very light. I have been below 20 degree's with 0 issues. Has held up great!


      I know there are a large amount of people out in the ultralight community that have different opinions on sleeping bags. For the type of hiking I do(alpine, variable climates,frigid nights and long treks) this is exactly what I needed. This bag is light, and is VERY true to its rating. If you want to rest assure this is your bag. Its pricy because it’s quality built. I do upholstery work on Hot Rods and I know quality hand stitching when I see it. These guys take pride in the work they do. Made in the USA!

      impressive quality and warmth

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

      Bought this as a gift for a friend and here's what he had to say: I didn't want to sacrifice warmth or weight, and this seemed to be the bag to get. Cursory impressions- fluffy, lightweight, toasty warm, packs down small, and great build quality all-around. Can't wait to test it on a trip!

      Packs as small as a nalgene!

      • Familiarity: I gave it as a gift but have feedback to share

      From my friend: This bag is light weight and with a compression sack, packs down to the size of a large Nalgene.
      It is a good bag for summer but 20 degrees is a stretch. Maybe 40 degrees for comfort even with a pad. Excellent quality. I am 6’3” and the long fits well. Recommend this bag for warmer summer temperature.


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

      I've eyed WM bags for three years, but getting by during the California drought with an old bag someone left in my car ;0. Alas the long winter finally came and where we were sleeping on dirt the past few summers, we're laying on the deep snowpack of the 2016-17 Winter.

      I snagged this bag on a Wednesday night with the help of a gearhead, got extra help to make sure I had it in time for my trip, THEN got a call the next day from my dedicated gearhead who set me up with a change in size to make sure I was getting the full 20degrees. Boy did I!

      Camping under the Palisade Glacier in my 4season tent, I was snug as a bug in this one. True to temp rating and fully able to go base layers only in a cold Sierra night (first time winter camping). Love the drawstring system, incredible build, packs light. Now just need a better stuff sack to fit in my smaller touring bag so I can keep skiing through the summer!!!

      5'6" in a 5'6" bag. perfect.



      • Familiarity: I've used it several times

      This bag is amazing - super light and packs up quite small. I took it on a camping trip where the lows were in the teens and was cozy all night. As someone who moves around a lot in their sleep, I appreciated the roominess in the shoulder and hip area so I could flip onto my stomach and not be twisted up like has happened with other bags in the past. I'll be a Western Mountaineering customer for life!

      Great bag!

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

      After much hand wringing, I decided to go for it and splurge on this top-of-the-line bag. So many strong recommendations from seasoned thru-hikers and backpackers that I knew I could not go wrong. It was a major upgrade over my 10 year old bag with the store-label of a direct competitor. That bag was listed as UL +10, but weights in >3 pounds and is really not much different than a 30-40 degree bag. In short, I twist, turn, and run cold in it a lot.

      Used this bag for 2 night trial run up in the High Sierras near Devils Post Pile NM. It was great. Packs down super well, light enough for the bag, and lofts up super comfy for bed time. I am SOOOO happy I now have a right zip as well. As a lefty and right-side side sleeper, this was a HUGE plus of the new bag. Makes things so much easier and more comfy. Plus the zipper is great and really avoided snags so it seemed.

      I have yet to test in cold weather, but trust it will work well. Got to about 45 both nights give or take. One night slept in shorts & T with light fleece top all zipped up. This was colder of the two nights and I was super comfy. Second night I was more acclimatized to the elevation and weather and ran in shorts and a T with bag unzipped almost 1/2 the night and used more as an open blanket. Again, VERY comfy.

      I was very nervous as a side sleeper that this bag may run a bit too narrow. I tried some competitor bags that did run narrow and returned it. The only next bag was WM Alpine Lite, but that felt a bit too much and was a touch more $ and weight. I erred on trusting reviews of the bag from so many others. And found that despite being a side sleeper, the bag still worked great. I am 5'6" or so and 160 so not too big, thus the 6 foot bag was fine and even let me toss and turn a bit.

      Also, even though teh bag does not have stays to keep in place on my air mattress, it did not roll around a lot with me. It held is position very well, which was also a huge added bonus.

      The bag was paired with a 3.2R rated Thermarest Neo Air X Lite. Combined I may have had the most comfortable camping sleep in ages, if ever. It just worked.

      I do have to be extra careful with the bag. It does appear sensitive. And may avoid using it for family camping fearful of my little ones jumping around on it. But for backcountry camping, it is the bomb. I am super stoked.

      And I love how well it will pack down in my pack. I was only stuff into a dry sack, but not a dry compression sack. It still packed down really well and handled the pressure of my bear canister on top of if really well.

      Super stoked. If you need a bag for the backcountry, this may be it. Very stoked for this bag. I know w serious TLC, it will last me a good 10-20 years of solid use.

      As Promised

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

      First AT section hike with the new bag. Can't vouch for the temp limit (did not get below 50's, so used it open as a quilt), but it's certainly light, packable and warm. The anti-snag tape for the zipper is a great plus. Pricey but hoping to get years of use from it. I'm small (5'8" 160) male and the fit was plenty spacious for me as a side sleeper.

      < 2lb furnace

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

      Took this bag out last weekend for an overnight at 10k ft. and about 40F. I was roasting. I had to hang an arm out of the thing most of the night. Had it not been for mosquitos, I would have probably just draped this over me.

      I had been slightly worried because my old 20F bag was sketchy below 40F and weighs over a pound more. The 850 is really amazing.

      My only gripe with this bag it that at 6'2" and 215 lbs it was snug. Not constricting, but a bit more snug than I'd like as a side sleeper, so I'm exchanging this for the TerraLite. I have no doubts the 5F loss in rating will affect me much, given how warm this bag was.

      Western Mountaineering and have won me over.

      < 2lb furnace

      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.

      Hey there - Thank you for the great review! Yes, the Ultralite is WARM, and a big reason is that it is a narrow and efficient bag. Not alot of dead air space to heat up! Awesome bag by Western!

      Western Mountaineering rep

      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.

      I try to compare this sleeping bag with some europeen supplier but i struggle :
      In Europe we use the norm EN 13537, wich specify :
      -Comfort temperature : women 60kg lying position
      -Limit Temperature (or limit comfort temeprature) : men 70kg Fetus Position
      -Extrem Temeprature : Risk of death

      In Us there is only the comfort temperature given : Is it comparable to our comfort temeprature ?
      What would be the Limit Temperature for the Ultralight Western Mounteinering sleeping bag ?

      Thx in Advance

      Hey Eric! Thanks for asking. I got the answer from our Western Mountaineering rep for you and also emailed you a copy of the entire catalog + EN ratings. To answer you questions here:

      1 Comfort rating: 25F or -4C

      2 Limit Rating: 14F or -10C

      3 Extreme Rating: -21F or -29C

      Please note that the EN 13537 standard temp testing produces inaccurate data for extreme cold weather bags.

      Hey Eric! Thanks for asking. I got the answer from our  Western Mountaineering rep for you and also emailed you a copy of the entire catalog + EN ratings. To answer you questions here: 

1 Comfort rating: 25F or -4C
2 Limit Rating: 14F or -10C
3 Extreme Rating: -21F or -29C

Please note that the EN 13537 standard temp testing produces inaccurate data for extreme cold weather bags.

      Is the fill weight, 16 oz, the actual weight of the bag? Or how heavy is it? And what's the volume of the packed/compressed bag? My current bag is 5 L and 856 g. Thank you!

      Hi Kyle the UltraLite has a fill wt of 15oz, 16oz and 17oz for the three sizes. The total wt are 1lb 12oz, 1lb 13oz, and 1lb 15oz for the three sizes. The stuff sack size is 8L. Let me know if I can help answer any other quetions for you on this sleeping bag or any others.

      Options! Love them, but I'm trying to figureout what will work best for me. I am typically a cold sleeper (female), I'm 5'7" 140lb, side sleeper but I roll around a lot in my sleep. I am leaning towards the Ultralite or Alpinlite. Would rhe short be too short for me? I don't want my bag to be less efficient i.e. cold if I go with the regular and end up with 5 extra inches around my feet. Wondering the same thing about the Alpinist vs. Ultralite in terms of wiggling around at night. Purchasing for my upcoming PCT hike. Thoughts? Thanks!

      Kendall, Good questions! IF you are ok with it being a little short, 1" to be exact, then go with the 5'6". it will be a little tight, but just a little. The Ultralite is NOT the bag for you, though, if you are like me: a wiggler! Absolutely go with the Alpinlite, hands down. The Ultralite is very narrow and efficient, but not much room to move around if you are a wiggler.

      Hope that helps!


      Western Mountaineering Rep

      The price?
      I have been wanting the WM UL for a while now but it is just too much money for me. Will these sleeping bags ever be on discount?

      Hi there - are you asking what the price is? If so, it depends on the length. If you are wondering why it's priced where it is, it is absolutely one of the best made bags, period. AND it's made in San Jose, CA... The production of these bags is limited, as is its distribution, so they never have excess, and there is no reason to discount.

      I hope there is a way for you to get into one of these bags! You will love it. Hit me up with any questions.


      Western Mountaineering Rep

      I'm 5'11", slender build, should I go with a 6' or 6'6" sleeping bag?

      Best Answer

      Hey Nate,

      I'm 6'2" and bounce between long and regular bags. I've found that since I sleep on my side often in warmer weather I can use regular bags but when I sleep on my back (usually in my winter bag) I need the length.

      So if you typically sleep on your side a 6' should be fine

      Hey Nate - I agree with Reid, the 6' bag should be fine for you. I am 6'1" and sleep on my side and tend to prefer a 6'6" bag for the extra room. Feel free to contact me directly with any additional questions.

      - Kyle L. - Expert Gearhead

      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?

      Best Answer

      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!


      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".

      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

      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?

      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


      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!

      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

      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...

      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.

      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).

      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?