If you're looking for a top-notch quality, lightweight, buy-it-for-life, made in USA backpacking sleeping bag, and you're stuck between Western Mountaineering Ultralite and Alpinlite, you don't need to worry because I can almost 100% guarantee you that you absolutely can't and won't go wrong with either of them. Both are warm, comfortable, lightweight, packed small and versatile - with one small difference:
Ultralite is just a slimmer version of the Alpinlite.
Everything else is the same although you get a 2 oz less weight and smaller packed size with the Ultralite's slimmer cut (see their manuals here [PDF]).
But how do you know which one you should get? In this post, I've gathered all the information to consider when deciding between Alpinlite and Ultralite.
You can only get Alpinlite 7' because the longest Ultralite is only 6'6".
First of all, as long as you aren't over 6'6", you probably won't experience any problem in fitting inside either of these bags (regardless of your shoulder width, build, etc). If you're a side sleeper, Alpinlite | $645.00 is probably a better choice for you since its baggier cut allows more comfort for side sleepers. For all the others, Ultralite | $580.00 is probably the better choice since its slimmer cut brings nearly smaller packed size (for sizes over 5'6" in length) and ≈2 oz of weight reduction.
But, again, both bags are top tier and I'd highly doubt you'd regret buying either of them.
Don't get either of these mummy bags and check out Nemo Disco/Rave/Riff/Jam spoon shaped sleeping bags which are specifically designed for this purpose. But beware - they aren't made in USA unlike Alpinlite and Ultralite.
I talked to the WM Customer Service (screenshot below) and concluded this once more: Ultralite is just a slimmer version of the Alpinlite. Everything else is identical!
Here's the mail attachment: https://outdoorcrunch.com/wp-content/uploads/2019/02/WM-2018-Specs-1.jpg
Now, the differences are as follows on paper:
- Width: Alpinlite is 4-5" (depending on the bag sizes - see attachment by the rep above) wider in shoulders & hips, and 1" wider in foot
- Weight: Alpinlite is 1-2 oz heavier (depending on the bag sizes - see attachment by the rep above)
- Fill weight: Being wider, Alpinlite needs 2 extra oz of down to offer the same warmth as Ultralite
- Packed smaller: Sack size of Ultralite is XS - whereas that of Alpinlite is S. However, 5'6" Alpinlite also comes in XS sack size.
And now let me translate the consequences of these spec differences.
Let's begin with the most important difference.
Extra girth of Alpinlite has a few advantages over Ultralite:
- Sleeping on your side/tummy (for some, even on your back!) is more comfortable
- You can stuff valuable or self-defense gear inside (be a lone female) when needed
- When it's below 20 F (which is the min advertised temperature limit for both bags) you can stuff pre-heated rocks inside for extra warmth, or you can wear more layer and still sleep inside comfortably
What about the downsides of extra width of Alpinlite?
- Depending on the bag size you get, it's 1-2 oz heavier than Ultralite
- Unless you get the 5'6" size, stuff sack is 1 size larger than Ultralite (S vs XS) (more on this later)
Wait, so the extra dead air in Alpinlite doesn't take longer to be heated?
Technically speaking, it should (does), but it really isn't noticeable at all. Inner volume increase really isn't substantial when it comes to heating speed.
I'd clear this out in my mind: Regardless of your build/gender/weight/height/age, you'll experience the same warmth inside these bags.
Which brings me to my next point...
Although the warmth provided by these bags are identical, I'd like to talk about some shared features of these bags.
If you're unaware what fill weight means: It's the weight (amount) of down used in the bag.
If you're unaware what down means, it's the feather that keeps duck and goose warm. As a thermodynamics law (entropy), the heat will always diffuse a colder region in order to achieve equilibrium. In that case, these feathers (down) traps the air inside and prevent the heat from escaping the heat source (which, in our case, is human body).
We humans use this down in sleeping bags, jackets, booties and in everything else we'd like to insulate and keep warm as long as possible.
Fill weight (amount of down) is directly proportional to the warmth provided by a sleeping bag.
Alpinlite has 2 extra oz of down. But! That does NOT mean that Alpinlite offers more warmth! Since it's wider, it has more material and therefore needs to have more down by right to provide the same warmth as Ultralite.
The warmth provided by these bags are identical.
What about Fill Power?
If you're unaware, fill power (FP) is what, ultimately, defines the quality of a down. It's rated on a scale from around 500 up to 900. A 500 FP down means that when the down is at rest, it'll spread to 500 cubic inches. The higher the volume it spreads, the more air is going to be trapped inside the down.
This way less heat will be able to escape your body, and as a result, you'll feel warmer.
Most other manufacturers equip their gear with downs with different fill power: 500, 600, 800. Although it certainly is possible to provide a fair amount of warmth using a low-end FP (low quality) down, it certainly will take a lot more of it and hence the heavier weight.
Western Mountaineering, on the other hand, always uses the finest quality down. They never use even medium-high quality down (below 800 FP). According to their manuals [PDF], their laboratory tests conclude their down quality over 850 FP. This is how they achieve low weight, small packed size AND incredible warmth all at the same time (hence their premium price range). This is only attainable with a super high FP - like 850+.
So if Alpinlite and Ultralite both offer 850+ FP (very high) down quality, that means they're identical. Then why am I talking about it?
- So that you know both use top-notch down quality
- It'll be important when I talk about the storage of these bags
Conclusion: Both bags provide equal warmth.
Also, these bags are rated at 20 F - which means they're going to provide enough warm at temperatures as low as 20 F.
What if you use them below 20 F?
This value (20 F) is not only conservative, but also indicate the minimum temperature a 25 year old, 5'3" (1.6 m) & 130 lb (60 kg) female can sleep comfortably inside the bag.
It's based on women since they sleep colder than men.
Although these are 3 season bags, they will still feel pretty warm even below 20 F. For even further below that, you can check out my 3 most effective tips to heat a tent/sleeping bag without electricity. The "heating rocks" tip would work the best with Alpinlite rather than Ultralite since it has more room inside to stuff items.
Weight and packed size
As you see, depending on the model, Alpinlite is 1-2 oz heavier than Ultralite:
To me (not really an ultralighter and more like a fairlighter) these weight reductions of UltraLite wouldn't really worth sacrificing the extra comfort and customization benefits of the AlpinLite.
Packed size (stuff sack)
Here's how XS and S stuff sack sizes compare:
As you see in the chart above, S size is 8 (DIA) x 15 inches, whereas XS size is 7 (DIA) x 13 inches. "Compressed volume" column you see in the above chart isn't important since both bags come with their stuff sack and you'll be using them for transport.
Another thing to consider here, as mentioned earlier, is the 5'6" size of these bags: They both come in XS stuff sack. So, if you're planning to buy the 5'6" size of either of these bags, Ultralite loses its packed size advantage!
ALWAYS push your sleeping bags to very deep into their sacks - but they should stay there only when transporting! Otherwise, your sleeping bag should always be stored in the storage bag - which is baggier and allows the down to breathe and stay lofty. This is very important for the life of your sleeping bag.
For other maintenance and FAQ, this guide by WM can be a good read for you.
Other shared features of these bags
Both bags offer the following.
This is what I really like about these bags as it allows great versatility.
Continuous baffle allows shifting the down at the top of the bag to the bottom of it (and vice versa) and as a result adjusting insulation (and hence, warmth) to your taste. What I really like about this is that you can basically sleep a lot more comfortably during warmer summer nights.
Therefore, unlike most other bags, you can use these bags during hot summer nights AND cold winter nights.
Draft tube hinders the heat leakage from zippers.
This draft tube helps the downs protect their full loft throughout the entire bag surface. This way, in terms of heat leakage, these zips aren't the weakest spot of a bag anymore.
What WM calls "full collar" is the continued portion of draft tube:
Just like draft tube, full collar also prevents the heated air from escaping the bag. But unlike around the zipper, full collar prevents the it from escaping it around your neck.
As you see, when full collar and draft tube is combined, you get a highly insulated sleeping bag.
Left or right zip?
As you see on Amazon, both bags come with either left or right zips. To me, this is only important if you own an asymmetric 1P tent which offers only one door. Let me tell you why.
Chances are, with that type of small tent, you'd probably want your feet pointed towards the end of the tent with smaller area while sleeping. So, with this sleeping bag position, if the door of your tent is positioned to the right of your sleeping bag, you'd better get the bag with right-zipping. If the door of your tent is positioned to the left of your sleeping bag, you'd better get the bag with left-zipping!
Also, if you're looking for an air mattress for camping too, this post of mine can be a good read for you.
In summary, I'd recommend the Alpinlite | $645.00 to all side/tummy sleepers and/or bigger fellas. If you aren't one of these, the ways you can leverage the extra internal room can still be substantial: You can always stuff valuable and/or self-defense gear inside when needed (especially if you're a lone camping female). When it's below 20 F (comfort limit for these bags) outside, you can stuff pre-heated rocks inside for more warmth, or wear extra layers.
If you're a slim person, though, and you aren't really a side/tummy sleeper, the extra room of Alpinlite could be a downside as it adds to weight. If you'd gladly take the 2 oz of weight reduction and smaller packed size (for sizes over 5'6") over all these benefits, Ultralite | $580.00 is the way to go for you.
Lastly, my other post how to sleep comfortably in a tent can be a good read for you.
I hope this review was helpful for you to understand which WM sleeping bag would be the best choice for your needs. Feel free to ask me any questions, provide feedback and I'll be happy to respond in the comment section below if it's within my knowledge.
Thanks a lot for reading. Happy trails.