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Western Mountaineering UltraLite

rated 4.0 of 5 stars
photo: Western Mountaineering UltraLite 3-season down sleeping bag

Lightweight, comfortable bag that's super warm. Highly recommended.


  • Lightweight
  • High-quality materials and construction
  • Under-rated at 20°F
  • Zippers never jam


  • Expensive

I've had this bag for about 6 months and have used it extensively on every outing I've done (including the entire John Muir Trail in Aug 2013). I don't think I've been below 25° yet, so I can't honestly attest to its lowest rating, however I have never been even close to being cold in this bag. Even sleeping inside it naked at 28°F in snow conditions I felt HOT all night.

I haven't noticed any drafts at all.

The (Large) fit is roomy for my 6'0", 170lb frame.

The zippers work perfect and NEVER jam because of a protective stripe of material near the zipper.

One night I accidentally spilled some water near my feet on the outside of the bag. I never felt the moisture on the inside of the bag and noticed no difference in it's insulating properties.

The stuff sack sold with it is lightweight and packs much smaller than my old synthetic 45° bag.

Loft is consistently puffy and big after just a minute out of the bag.

Overall, the materials and construction are of an unsurpassed of quality.

I would highly recommend this bag to anyone.

Source: bought it new
Price Paid: $449.95

I use a WM Antelope for fall and early winter camping and the UltraLite for everything else. Lightest and warmest 20 degree bag I've ever experienced. At 1lb 12oz and 850 fill, this long version sleeping bag stuffs into the smallest stuff sack for maximum compactness. However I've recently been stuffing it into my day pack with all my other down items and clothes, etc.

This package fits neatly into the bottom of my pack without compressing the down as much as other methods. I don't like using compression stuff sacks for 850 like I used to for 550 and 600. Just a personal thing. I'm 6'3" 185 lbs with plenty of room to spare in the WM UltraLite. No half zip here. Full zip for maximum ventilation and roomy foot box. In my opinion, Western Mountaineering is the "Magnum Opus" of sleeping bag manufacturers!!!

*Highly recommended for people in good mountaineering shape. Not recommended for gorillas!!!

Design: Mummy
Fill: 850
Temperature Rating: +20
Weight: 1lb 12oz

WM makes a great bag. The ultralight series is pretty amazing, makes you feel warm just pulling it from the stuff sack. It keeps me warm at well under the 25 deg rating, huge amounts of loft, and the fabric is surprising water resistent. The outside can get quite damp and the down will be perfectly dry. Even covered with heavy condensation my WM bags have never lost loft.

Design: Mummy
Fill: 750 fill down
Temperature Rating: 25 F
Weight: 25 oz on my scale
Price Paid: $300

This incredibly light bag is super warm, and compact. I think it's THE summer bag to own, especially if you usually camp in dry climates. Very solid construction, impecable stitching, box bafflles, draft tube, this bag is well down. In fact it's warm enough to warrant a neck draft tube as well, because you could venture into colder climes with this bag.

Design: mummy
Fill: 700 fill down
Temperature Rating: 20 F
Weight: 2 lbs
Price Paid: $375 can.

I purchased this bag as I found my other high quality down bag -1'C not to warm enough in 4'C temp in my bivy with merinos on. The WM Ultralite was just excellent in the same conditions perhaps even cooler windy temps with a NeoAir under neath.

It's light, compact and fits my 185cm 90kg frame well.

Just got mine used and I'm super impressed. So light, well made, a bit tight at five nine, one fifty five. It's my new three-season bag. The Iroquois goes for summer now and the Badger is for colder nights.

Design: mummy tight
Fill: 750
Temperature Rating: 25
Weight: 1lb 12oz

I have a lot of bags...
This is the worst one.

All my bags the temperature rating tends to be conservative, but in this WM bag the rating is hyped.
I am a very warm sleeper, I can do well in most bags even though the temperature has dropped below its recommended use.

Not with WM Ultralight... For the first time I was freezing in a bag that was rated at about the temperature I was in.

WM attempts to create a lighter bag by making the bag smaller and less down filled then other bags. Their specs don't seem to match the actual construction of the bag. I found this bag to be very tight around the shoulders and very cold.

I have bags by Mountain Hardwear, Marmot, Campmor and Western Mountaineering. Either the other manufacturers are very conservative about their own product specs OR Western Mountaineering is way TOO generous on their own specs.

Above all I feel their products are over priced considering these flaws. And I am at a total lose why others gave them a perfect score. Why?

Design: mummy
Fill: 850 down
Temperature Rating: 32
Weight: 1 15
Price Paid: $350

The coldest 20-degree bag ever sold


  • is a sheet...and just about as warm


  • Cold........DAMN cold
  • Expensive!

I've never been so disappointed in a product.....ANY product by ANY manufacturer. Previously had a nice warm 20 degree Blue Kazoo from North Face, however I washed it and it was never the same. I bought this 20 degree  bag as a replacement,  and in an effort to reduce weight.

Used it during a JMT thru-hike in mid-August 2012. Froze my ass off every night, all night, no matter what the elevation. How anyone could rate this bag as comfortable below 35 degrees, much less 20 degrees is beyond belief.  Immediately after finishing the JMT, I returned to the retailer from whom I bought this POS and angrily demanded my money back, which, to their credit, they refunded in full...thanks a16. 

Source: bought it new
Price Paid: $400

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short regular long
Price Current Retail: $496.00-$600.00
Historic Range: $200.20-$600.00
Reviewers Paid: $300.00-$449.95
Weight 1 lb 12 oz / 790 g 1 lb 13 oz / 820 g 1 lb 15 oz / 870 g
Fill weight 15 oz / 425 g 1 lb 0 oz / 450 g 1 lb 1 oz / 480 g
Loft 5 in / 12.5 cm 5 in / 12.5 cm 5 in / 12.5 cm
Temperature rating 20 F / -7 C 20 F / -7 C 20 F / -7 C
Fill 850 fill-power down 850 fill-power down 850 fill-power down
Shape Mummy Mummy Mummy
Max user height 5 ft 6 in / 165 cm 6 ft 0 in / 180 cm 6 ft 6 in / 200 cm
Shoulder girth 59 in / 150 cm 59 in / 150 cm 60 in / 152 cm
Hip girth 51 in / 130 cm 51 in / 130 cm 52 in / 132 cm
Foot girth 38 in / 97 cm 38 in / 97 cm 38 in / 97 cm
Product Details from Western Mountaineering »