Western Mountaineering UltraLite 20 Mummy Sleeping Bag Review

8.8 score
[Editors rating (8.8)] = (Gearweare.net) score (8.8)/10

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Editor rating: 8.8 / 10
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Editor’s Conclusion
Western Mountaineering’s UltraLite 20 boasts a lot of great benefits, one of the most impressive being its warmth. This brand is transparent about its temperature ratings. Depending on your tolerance, you may even be able to use this item in temperatures lower than 20 degrees. It is a three-season bag that is lightweight (considering what it delivers), mummy shaped, and decently compressible.

The 20 denier material is inherently water-resistant, but the down fill was not treated with a hydrophobic treatment. This means that you will need to be more cautious than normal if you encounter rain. If the down fill gets wet, the insulation qualities will not be effective.

Now that I’ve introduced you to the two biggest strengths and weaknesses of this product, there’s a lot more to learn! Keep reading to discover more advantages (and a couple disadvantages) of this USA-made sleeping bag.
Western Mountaineering UltraLite 20 Mummy Sleeping Bag Review Review Facts
Editor's Pros & Cons


Provides great warmth

Full length 2-way zipper

Made in the USA



No ventilation zippers

Included stuff sack doesn’t compress the bag enough

No DWR finish

Key Features


If you’re planning to pack the Western Mountaineering UltraLite into your hiking backpack, it may prove to be difficult. However, if you’re planning to attach it to the outside, you’ll be alright. When stuffed into the included sack, it measures 7” by 13”. To be honest, the stuff sack from Western Mountaineering is not impressive. I recommend purchasing a different one with stronger compression abilities. With a bit of patience and elbow grease, you can get it crammed into a seven-liter bag.

As for the weight, the regular-sized sleeping bag weighs a little under 2 pounds. While you may not be initially impressed by this weight, for the amount of warmth that it provides, it is quite lightweight. A durable storage sack is also included for packing it away in the off-season.


In terms of comfort, remember that this is a mummy bag. This means that your only option is to sleep on your back. There isn’t much room to move around and you’ll likely feel restricted. To be exact, the regular-sized UltraLite has a shoulder width of 59-inches, 51-inches of width at the hips, and 38-inches of width at the feet. It definitely feels snug around the shoulders, but the tightness is necessary to keep in the warmth.

The fabric feels soft against your skin. Unfortunately, there is no built-in pillow pocket, but I don’t see that as a deal-breaker. As long as you don’t mind a lack of freedom, you’ll be quite comfortable in this sleeping bag. Although it is not advertised by Western Mountaineering, two bags can be zipped together if you want to sleep with your partner. You can choose to purchase this item with a left or right zipper.


When Western Mountaineering puts a temperature rating on a product, you can trust it. This 20-degree sleeping bag has 16-ounces of 850 down fill. The down collar is ample and can be cinched tightly around your shoulders for added warmth. The hood and collar also have velcro tabs that allow you to create a tight seal. However, with such limited space to move around, it can be difficult to maneuver the velcro and cinch.

One of the best, and warmest, features of this product are the continuous horizontal baffles. They are spaced 5.25-inches apart. On nights when you need less insulation, you can move the insulation to the bottom of the bag, allowing the heat to escape. On colder nights, you’ll be happy to have the insulation on the top.

This 3-season bag works wonders in cold climates. Depending on how your body regulates its temperature, you could even use it in 10-degree weather. However, in warm climates, you might overheat a bit. One saving grace is the two-way zipper which gives you the option to let some air into the bottom of the bag. Thermal zippers on the side of the bag would be much appreciated.


The fabric used to make the UltraLite is soft and comfortable against the skin. The exterior shell is made from 20 denier fabric. The full-length #5 YKK is smooth and reliable. If you camp in inclement weather, you will want to be sure to have a weather-resistant tent and to use a tarp. The goose feather down fill is not finished with a hydrophobic treatment, meaning it doesn’t repel water very well nor does it dry quickly.

In better news, the goose feathers are sustainably sourced. This ensures the humane treatment of the animals and the feathers can actually be traced back to the animal. The shell of the bag is strong enough that I don’t expect water will seep through easily. If water does get through, you will not be able to depend on this bag to keep you warm. Do your best to keep it dry.

The velcro tabs on the hood that I mentioned earlier are strong and work well to keep the hood sealed. The cinching string is also made from a strong and reliable material.


While I don’t have any complaints yet, the 20 denier fabric shell does slightly concern me. Considering a 1 denier fabric has the thickness of a piece of silk, 20 denier is still fairly thin. Like I said, this hasn’t been an issue thus far, but we will see how it holds up.

It’s not all bad though. Western Mountaineering has great customer service and also provides a lifetime warranty against manufacturer defects.

Comparison to Similar Sleeping Bags

Nearing the top of its class, there are a few sleeping bags from Western Mountaineering that are commonly compared to the UltraLite. They include the AlpinLite, the TerraLite, and the VersaLite.

The AlpinLite 20 is very similar to the UltraLite but it is wider. If you don’t love a tight mummy shape, this would be a better option. However, because it is roomier, it is also heavier and slightly more expensive.

The TerraLite 25 provides slightly less warmth than the UltraLite but also has 850 down fill power. The outer shell is made from 12 denier ripstop and it also weighs in at 1.13 pounds. There are extra inches of fabric sewn in, making this a great option for side sleepers. The thinner denier material makes this option slightly less durable.

The VersaLite 10 also has 850 down fill power, but has a temperature rating of 10. The collar of this bag is even grander and warmer than that of the UltraLite. It is also a mummy-shaped bag that doesn’t leave much room for movement. The extra warmth provided also tacks on a few extra ounces. This one weighs in about 2-pounds.


Overall, I’d say this is a good investment for cold-weather campers. The warmth rating and the impressive draft collar hold in a lot of heat, which may actually be unnecessary for some seasons. If you tend to camp in the hot summer months, this may not be the best option for you. The only way to cool yourself down is to unzip the bag. Also, remember that this is a mummy bag, which does restrict your movements.

One other fact that can not be ignored is the price of this sleeping bag. It is a hefty investment but comes with a lifetime warranty. If you take care of the UltraLite, it will take care of you.