Western Mountaineering UltraLite Sleeping Bag Review

I tested the Western Mountaineering UltraLite sleeping bag and this is my verdict.

June 13, 2024
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Western Mountaineering's UltraLite mummy sleeping bag is renowned for its exceptional warmth-to-weight ratio, featuring 850+ fill power ethically down-packed into a well-thought-out design and 12D ripstop nylon. The UltraLite ditches fancy features, such as pockets, and instead delivers a functional product meant to keep you warm on any adventure.

Product Overview

Western Mountaineering UltraLite Sleeping Bag

western mountaineering ultralite sleeping bag

✅ Warmer than the stated 20F rating

✅ Lightweight

✅ Made in the USA with ethically-sourced Down

✅ Durable

✅ Packable


❌ Expensive

❌ Not as light as some quilts


  • Shape: Mummy Style with a Full Collar
  • Total Weight: 1lb 13oz (6'0")
  • Temperature Rating: 20° Fahrenheit
  • Fill: 850+ Power Goose Down
  • Fill Weight: 16 oz (6'0")
  • Length: 5'6" (165 cm), 6'0" (180 cm), 6'6" (200 cm)
  • Fabric: 12D ripstop nylon
  • Loft: 5.5” in

Quilts have been all of the rave in recent years. It is unmistakable that you can shed weight by removing a third of the material with a quilt. Western Mountaineering sells quilts which I am sure adhere to their reputation. I am a bit old school in that I love a traditional sleeping bag.

Based on discussions with other hikers, I have found that quilts are even less reliable when it comes to the claimed temperature rating. If you pair the Western Mountaineering UltraLite with a similar quality sleeping pad, then you will not be disappointed. If you are considering an adventure where functionality is of the utmost importance, then you should further research this product to see if it fits your needs.

To see reviews on other ultralight sleeping bags, see our post on the best ultralight sleeping bags.

Performance Test Results

How We Tested:

I used the UltraLite sleeping bag for roughly 100 nights during my SoBo AT thru-hike. In addition, I have used this bag in places across the country for a number of multi-night backpacking and camping trips. Primarily, this bag has been used on the low-elevation damp trails of the East Coast, but it performs even better in dry conditions. Many people choose synthetic fills for AT thru-hikes, but I found this bag to be extremely effective even during rainy days and nights.


How does Western Mountaineering charge $600+ for some down trapped in nylon? If you aren’t able to sleep in a sleeping bag filled with money, then this is probably the first question that comes to mind. Rest assured, Western Mountaineering is not price gouging you and they are well aware that many customers will go to more budget-friendly options.

The price is the biggest con of this product, but it is that high for a few reasons. Firstly, and most importantly, is the quality. Western Mountaineering makes products proudly in the USA and from the highest quality materials on the market. You are getting a product that the company, employees, and end users are proud of.

The down is ethically sourced, which means that there is minimal harm to the animals that produce it. Each bag has the signature of the employee that worked on it. My mother is a home economics teacher and could be a professional seamstress. She has instilled in me, and, has firsthand shown me, the importance of textile construction, stitch quality, and the knowledge that it takes to get it right.

western mountaineering ultralite sleeping bag
The UltraLite sleeping bag retails from $600-$635.


The second reason is that Western Mountaineering produces a product that outperforms the baseline specifications they list. I cannot count the number of times that I, a friend, or a fellow hiker have complained that their bag is not as warm as the specified temperature rating. This is not the case with the UltraLite sleeping bag. I have personally slept below 20F with high winds and had absolutely no issue staying warm.

Without mentioning other manufacturers, I have not had this experience with the majority of the other sleeping bags that I have purchased. This is mainly because most manufacturers list the absolute minimum limit temperature rating that their bag can withstand. Essentially, most bags claim a rating at which you wouldn’t die from freezing at the rated temperature, but by no means would you be warm at said rating. To me, a transparent bag rating is far more useful and true to the company's values.

western mountaineering ultralite zipper guard

One of the first times I used this bag was during a massive snowstorm in Virginia, near McAfee Knob. A buddy and I chose to do an extended weekend trip in the middle of winter. On the second day, snow began to fall in inches by the hour. It quickly turned into whiteout conditions with strong winds.

We found shelter in a lean-to along the AT and waited out the nearly 24-hour long storm. Snow was blowing through the sides and covered everything, melting as it warmed from our body heat and breath. Temperatures were 10F without the windchill. I stayed warm the entire time and the bag repelled water droplets well. At the end of that trip, I was sold.

western mountaineering ultralite zipper
The UltraLite's exceptional features, which I love is its flawlessly moving zipper.


The UltraLite is not a winter sleeping bag, but it can handle the majority of seasons along much of the East Coast. This obviously excludes winter conditions that can commonly be found in the Whites or more Northern states. Beyond that trip, I’ve had nothing but positive experiences using the UltraLite bag.

Furthermore, many ultralite products come with the disclaimer that they will wear out faster than their heavier counterparts. I have not found durability to be an issue with this product. I have spent over 150 nights sleeping in this bag and the nylon does not show noticeable signs of wear.


Apart from the functionality of the UltraLite, the sleeping bag is worth the money because of the materials used. Western Mountaineering claims 850+ fill power and they mention that 850 fill is generally an underestimation. If you have ever purchased a down product, then you know that fill power is the main driver for cost. The higher the fill power, the better the loft will be.

A budget bag will generally have a fill power of around 600. Anything above 800 fill is considered good in my experience. A sleeping bag has significantly more down compared to say a jacket, therefore higher fill power bags cost a lot in materials. Likewise, down itself is more expensive than a synthetic material. You get what you pay for. Down is 35% lighter than synthetic materials, packs down better, and lasts longer.

western mountaineering ultralite compressed size

Design and Features

The final reason is that you are paying for a well-designed product. The UltraLite is not just some down trapped in nylon. Western Mountaineering took careful consideration in the design. You can read all about their design choices here, but I will detail a few of the more important ones.

The UltraLite features a full collar, continuous baffles, and a draft tube in its design. The full collar blocks warm air from escaping through the neck region of the sleeping bag. A drawstring allows the user to cinch the collar when needed. The continuous baffles allow for the down to be shifted around in the sleeping bag. This is important since the bag is meant to be used across multiple seasons.

western mountaineering ultralite outdoor

Compressed down does not insulate well, therefore any down that is underneath you while sleeping does not help to keep you warm. This is why many people choose to go with quilts, where the bottom portion of the bag doesn’t exist. With the continuous baffles, you can put more down underneath you to stay cool in warmer temperatures.

More importantly, you can shift more down above you in cold temperatures to stay warm. The draft tube acts similarly to the full collar in that it stops warm air from escaping, but this down-filled feature blocks the zipper region. All of these features improve the efficiency of the UltraLite.

western mountaineering ultralite collar draft tube
The full collar blocks warm air from escaping through the neck region of the sleeping bag.

Final Thoughts

This sleeping bag isn’t meant for anyone on a budget or looking to go camping a few times a year. The target buyer is someone who needs this level of warmth, quality, weight, and packability. This includes mountaineers, thru-hikers, experienced weekend warriors, and anyone else who desires to push limits that require advanced gear.

I would not recommend this bag to a new backpacker or someone who is planning to go on a single trip. I completed many difficult backpacking trips with sleeping bags much heavier and of worse quality before embarking on my thru-hike. That being said, if you have the money and reason to purchase this bag then it is worth every penny.

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Drew Flickinger photo

About Drew Flickinger

Drew completed a SoBo thru-hike of the AT in 2022 and is an enthusiast of Type 2 fun. He now spends his weekends exploring the outdoors in Pennsylvania with his wife and dog. 


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