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Western Mountaineering
Alpinlite Sleeping Bag: 20F Down

4.222222222222222 out of 5 stars
9 Reviews
$670.00 - $715.00



Why We Like The Alpinlite 20 Down Sleeping Bag

Climbing or traversing technical pitches with a massive load dangling behind you is a bad way to go through life. We recommend the Western Mountaineering Alpinlite 20-Degree Down Sleeping Bag for alpine climbers and weight-obsessed backpackers who demand top-shelf quality and bottom-line weight savings.

We love how its 850-fill down insulation boasts one of the highest quality loft-to-weight ratios around, meaning it's surprisingly warm for how little it weighs. Western Mountaineering wrapped this insulation around a highly breathable shell to keep the down light and lofty when you're sleeping in a tent under a rainstorm.


  • Ultralight sleeping bag designed for alpinists and backpackers
  • Breathable shell fabric keeps down lofty
  • 850-fill down provides a high warmth-to-weight ratio
  • Continuous baffles and a down-filled collar prevent cold drafts
  • Wider shoulder girth allows for extra layering in cold environments
  • Western Mountaineering bags are made in the USA
  • Item #WES0041
[face fabric] ExtremeLite, [lining] nylon taffeta
850+ fill down
full-length YKK #5
Max User Height
5ft 6in, 6ft, 6ft 6in, 7ft
Shoulder Circumference
[5ft, 6in] 63in, [6ft] 64in, [6ft 6in, 7ft] 65in
Hip Circumference
[6ft] 55in, [5ft 6in, 6ft 6in, 7ft] 56in
Foot Circumference
[5ft 6in, 6ft, 6ft 6in, 7ft] 39in
Bag Length
5ft 6in, 6ft, 6ft 6in, 7ft
Draft Tube
Pad Retainer
Fill Weight
[5ft 6in] 1lb 1oz, [6ft] 1lb 3oz, [6ft 6in] 1lb 5oz, [7ft] 1lb 7oz
20 F
European Norm/ISO Comfort Rating
European Norm/ISO Lower Limit Rating
Storage Sack
Stuff Sack
Stuff Size
[5ft 6in] 7 x 13in, [6ft, 6ft 6in, 7ft] 8 x 15in
Claimed Weight
[5ft 6in] 1lb 13oz, [6ft] 1lb 15oz, [6ft 6in] 2lb 1oz, [7ft] 2lb 4oz
backpacking, alpine
Manufacturer Warranty

Overall Rating

4 based on 9 ratings

Review Summary

1 Stars - 1 reviews
2 Stars - 1 reviews
3 Stars - 0 reviews
4 Stars - 0 reviews
5 Stars - 7 reviews

Fits True To Size

Screen reader users: the following list provides a visual scale to illustrate the product fit. Please refer to the heading above for the fit type in text.
Runs smallTrue to sizeRuns large

What do you think about this product?


Selecting an option will reload the available reviews on the page
5 out of 5 stars

June 14, 2024

The two reviews from 2021 are odd...

I've put it through the wringer
Size Bought:
6' 1"

Maybe Western Mountaineering was having issues in 2020/2021 due to Covid, but my 2024 is an absolute masterpiece. Consider this. The bags are full sleeping bags that are true to temp if not conservative, but they're only 2-4oz heavier than quilts. I'll find a way to save 2-4oz somewhere else and take a real sleeping bag, especially under 30F/0C Something not widely known! --> Western Mountaineering makes a bag extender that makes the bag more roomy and fits all their sleeping bags.

m m29
5 out of 5 stars

May 13, 2024

This is a great bag

I've used it once or twice and have initial impressions
Size Bought:

Used it once so far, and it was only about 40 F outside, so didn't really give it much of a test in the temperature where it's supposed to be capable. But, love the feel and the comfort of the bag. The draft collars are awesome, too. Pretty sure it'll be toasty at least close to its rating. I've kind of given up on quilts; I understand the thermodynamics of down - this just prevents the drafts that the quilt straps couldn't overcome for me. And I think it'll be wide enough for me to move around and side sleep well enough.

5 out of 5 stars

January 22, 2023

True to temp

I've used it several times
Size Bought:
5' 10"

This bag is incredible! Bag is definitely comfort rated to 20 degrees. I have used it in 23 degree weather with a 3 season tent and was comfortable. The design of being able to shift the loft is really helpful. Neck collar and hood system work well to completely remove drafts. It’s expensive no getting around that, but what you get in price is something that will last, as well as work in conditions advertised. The weight is light. This is my best piece of gear and I love it. I have used it 4 times since I purchased it 2 months ago.

Alexander K
5 out of 5 stars

August 24, 2022

Ultimate Cozy Goodness

I've put it through the wringer
Size Bought:
6' 3"

Easily the best sleeping bag I've ever owned. My previous down bag was rated to 16 degrees and was from a reputable manufacturer. With the old bag, I was comfortable down to about freezing (I'm a very cold sleeper). After using that bag for ~8 years, I decided to treat myself to an Alpinlite. The purchase hurt a little, but the bag is better than my old bag in every way. It is 1 pound lighter, and packs to probably 2/3 of the size. It is the same weight and packed size as a budget 40-degree summer down bag that I have. It is also much roomier. I'm a 6'3" dude and the Alpinlite is the first sleeping bag that I've felt was truly big enough to be comfortable as I toss and turn at night. The zipper has never ever snagged on me, and is the first sleeping bag zipper I can confidently use one-handed. As far as its performance, I can use it (with a proper pad) down to the low 20s with only shorts and a t-shirt on. With proper baselayers and socks, it goes down to about 18 degrees comfortably. Colder than that, I've use down booties and a 50 degree synthetic overquilt and taken it to 6 degrees, albeit I did get chilly (but I was using a subpar pad). Some have complained of the durability of the fabric, but I took this bag on a 6 week trip to Alaska involving over 20 nights of camping, and I had no issues. It is ultralight fabric, but as long as you don't abuse it, it will treat you well. Keep it away from pointy things and tent zippers. If you're really rough on your gear, maybe look at the WM Badger MF, which has a beefier fabric. It took about 30-40 nights of camping for it to start to smell, but your mileage may vary depending on your personal hygiene. The only true downside I've found with the bag is that it takes FOREVER to dry. Probably 8+ hours in the dryer on low heat. But this is due to how delightfully fluffy the down is, so it's worth it in my book The expense is also notable. I don't believe the saying "buy once, cry once" when it comes to Western Mountaineering. Because once you buy one bag, you'll love it so much that you will want two or three more, for different temperature ratings. I have no doubt the Alpinlite will last me well over a decade, if not longer, but I love it so much that I'm now in the market for their 0-degree bag :( I cannot recommend this bag and this company highly enough

Atlin J
5 out of 5 stars

August 2, 2022

This is a very warm comfortable bag

I've used it several times
Size Bought:
5' 10"

Some of the reviews have stated this is not a warm bag. WHAT? If it is 40 degrees or above it is actually too warm. WM bags are very conservative in their estimates. I love this bag. So plush, well made and very warm. As I stated above, for higher temps I would actually go with a less warm model of a WM bag. WM bags are worth the money!

Devin U
Alex QGearhead
5 out of 5 stars

July 15, 2022

Cloudy Warm Dream

I've put it through the wringer

I've spent at least 40 nights out in my Alpinlite and I haven't had a cold night of sleep once. Even down to 10 degrees I've been warm as a bug in a rug. Anything over 50 degrees and I'm sometimes sticking one leg out to cool off. The bag packs down to about the size of a nalgene +15% and is extremely light. The loft on the down is awesome and it's extremely cozy and airy feeling.

1 out of 5 stars

October 30, 2021

A bag of cold disappointment

I had been dreaming of getting the "ultimate" of°sleeping bag brands for more than a decade, and after much deliberation and research, I finally pulled the trigger on the Alpinlite. My very first night backpacking°with it, the tent zipper snagged the outer fabric and ripped a hole in it (an indication of how delicate the shell fabric is). I nearly sobbed. I was able to return the bag, and I purchased another of the same bag. When I recieved the new bag, I immediately noticed it wasn't as lofty as the first bag I had, especially in the chest area. This concerned me, but I decided to try it out anyway. I used it on a weeklong trip in the Wind Rivers, and I was cold and uncomfortable every night. And oddly enough, my legs and feet were somewhat°warm enough, but my upper body was freezing. The first night the temperature was 39°°(I had a thermometer in my tent), and I was cold all night. The following few nights were in the low 40's, and I was uncomfortable enough that I didn't sleep well. I used this bag for 6 nights, and not once was I comfortable.°For reference, the pad I used was the Nemo Astro Lite insulated, with a temperature rating of 15°-25° F (Nemo didn't use an R-value for this pad. Also, I've used this pad for years and have never been cold with it). Each night°I wore thick,°warm socks, long thermal midweight°underwear, and a beanie. This is the same combination that I've used for years with my previous bag (a Marmot Pinnacle) and I've never been as cold as I was in this bag. I even tried shifting more down to the top baffles of the bag, but it didn't help. I also noticed there were many spots where there was no down, and I could essentially see through the shell material. So, I either got a lemon, or Western Mountaineering's quality control sucks (I weighed the bag on a gram scale and it was under spec, which indicates it was under filled). Or, this bag doesn't°live up to the WM hype. Either way - and most of all - I'm really extra°ticked I dropped $600 on a stupid bag that doesn't keep me warm. Oh, and one more gripe: this bag has a tiny hood. I like to use a pillow stuffed in the bag's hood, but the hood is too small for it to work well.°So, don't believe the hype, steer clear and save your coin. You'll thank me you did.° Side note: dealing with Backcountry is the worst. I returned the bag and was expecting a refund, but they would only issue store credit (and never notified me). Chatting with their "woke", millennial°"Gearheads" -°who refer to you as "dude" or "man" -°is an excruciatingly painful and time-consuming ordeal. Thanks, Backcountry, but no thanks. I don't want to purchase anything from you. Oh wait, I have to because you're holding my money and are forcing me to. If I were you, I'd get off this site right now. Alex, they issued me store credit, which is different than a refund, especially when I don't want to buy anything from Backcountry. Ever. Also, I had no idea I recieved any store credit because they never emailed me and the mobile site doesn't show any credits anywhere. P.S., my disdain for Backcountry has no bearing on my review for this bag - it truly is a one-star bag (at least the one I recieved).

2 out of 5 stars

February 27, 2021

Good to 40 degrees at best

I've put it through the wringer
Size Bought:
5' 9"

I purchased this bag about 5 years ago don't get out as much as I would like but when I get a chance I go no matter what the temp, first time used bag early season bow hunting temp got around 35 F. nearly froze to death had to get up in middle of night get dressed go for a hike to warm up, took sleeping bag back to store manager said he would take bag back. I explained my situation with it that my back froze. He'd showed me that the bag has no baffles and you have to shake the down to the proper place, so I tried that with a little better result. Seems to me bag has great fill in toe box, neck curtain and head with very little on torso area. I use bag in 4 season tent with heater now and as long as I run heater all night long I'm comfortable.

Richard H
5 out of 5 stars

July 4, 2020

King of the Mountain

I've put it through the wringer

The needs of the backpacker are many, and often unreasonable. This bag weighs 2 pounds and for comparison some other things that weigh about 2 lbs include a small bag of rice, maybe a carton of milk, a desk lamp. For that little weight you get what is in my opinion, the best sleeping bag on the market. What makes this bag stand out? First off, the brand name carries all the accolades and associations it deserves. The sourcing (ethical sourcing with audits twice a year), water repellency, and hands on/in house processes are second to absolutely none. My bag's even signed by the person who stitched it (thank you by the way). The 850-fill down (a conservative estimate) kicks in like a human tortilla sized toaster oven. It is a 2lb space heater. Up to the draft tube and cinchable collar, this is a cloud of down designed to make sleeping while camping nicer than a night in your own bed. I don't think it would be possible for me to wake up grouchy or unsociable after a night's sleep in this so this is a gift to your camping buddies too! The only downside is the willpower I have to muster up to leave my portable sleep machine. It's the little details that make this feel as if your best friend made it given unlimited time and resources. The 20 degree rating is conservative for one thing. I run warm but I was very comfy in this bag at 7 degrees with the right liner and sleeping pad (PS please invest in your whole sleep system). The zipper simply does not catch. I had to do some research on the abilities of the benefits of a continuous baffle and I thought WM's site put it best "On a warm night slide down below you for less insulation, and on a cold night slide more to the top for warmer sleep!" Works just as advertised based on a warm California trip and a cold Oregon one. I camp quite a bit but I?ve only owned one sleeping bag before the Alpinlite. I dealt with many of the downfalls of a cheap sleeping bag - made with synthetic material rather than down so it couldn't pack as well and weighed more than it should. The zipper caught. Poor warmth compared to the temperature rating. I've tried out and borrowed at least a half dozen other bags without being blown away by any since that one gave out. After much, much, probably too much research I decided on the Alpinlite as a buy once, cry once panacea to my outdoor needs. My inaugural trip with this bag was a 2 day trip up to King's Peak. This gift to lovers of the outdoors was toasty, wide, and like the embodiment of a warm hug. It hardly takes up any space in my pack and the weight is negligible. I knew immediately I had made the right purchase. The price tag will undoubtedly throw people off, as it did me initially. I can say I've gotten my money's worth and more though. The quality of sleep, warmth, and the care that went into construction are simply outstanding. This is the bag I?ll be using for many years to come. Update a year later: still going strong! This bag is my best friend in the times of covid. No signs or wear and no regreats.

user image
Ben W