Western Mountaineering Puma MF Sleeping Bag : Minus 25 Degree Down

 Western Mountaineering Pum MF -25 Down Sleeping Bag

The Western Mountaineering Puma MF down sleeping bag is rated for negative 25 degrees F and is a fully-featured winter sleeping bag suitable for most winter backpacking trips in the lower 48 where you can expect to experience subzero temperatures.

Western Mountaineering Puma (-25) MF Sleeping Bag



Like all Western Mountaineering sleeping bags, the Puma is filled with 850+ fill power goose down which has a very high warmth to weight ratio. Weighing just 3 lbs 7 oz, it's also one of the lightest sleeping bags you can buy with this temperature rating on the market today.

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Like all Western Mountaineering sleeping bags, the Puma is filled with 850+ fill power goose down which has a very high warmth to weight ratio. Weighing just 3 lbs 7 oz, it’s also one of the lightest sleeping bags you can buy with this temperature rating on the market today.

Feature-wise, the Puma has two large down-filled draft tubes on either side of the zipper to block heat loss and a very comfortable draft collar that wraps around your upper chest and behind your neck to keep warm air from escaping your bag when you move around at night.

Hood of a Western Mountaineering Puma Ultralight Down Winter Sleeping Bag

The hood is spacious and comfortable and easily fits a down or primaloft pillow if you want a little extra comfort. My model here, on leave from Warmlite, is posing with a stuffed moose. The moose is not included with the bag and must be purchased separately.

Sizewise, the regular 6 foot bag has a shoulder/hip/foot circumference of 64/55/39 inches, making it a moderately snug around the shoulders and upper body for a 200 lb man. However, I was still able to stow some damp gear in my bag to dry overnight, including my plastic boot liners and gauntlet glove liners without being overly crowded.

Western Mountaineering Puma MF in Compression sack

The Puma also compresses down to the size of a basketball in a compression sack. This is significant. If you do any winter camping or mountaineering, you know that the size of your sleeping bag is directly proportional to the size and weight of the backpack you need to carry, since it takes up about 50% of the space in your pack. I bought the Puma expressly to make it possible for me to use a 4000 cubic inch backpack that weighs under 4 lbs for winter hiking and camping instead of a 5500+ ci pack, saving myself at least 3-4 lbs of base weight in the process.

Finally, the microfiber shell on the Puma, which is what the MF stands for, rocks. It is extremely water-resistant but highly breathable and given it’s weight to performance ratio, I feel that it is a better shell for my purposes than Gore-Tex Windstopper (GWS), another shell option that WM provides for the Puma.

On my trip, last weekend, three of us slept in a double-walled multi-person tent and we had a lot of tent condensation. My companion’s bags got quite wet, but my Puma was completely dry, which I attribute to the microfiber shell and its ability to repel water. In fact, I wish that my 3 season WM Ultralite 20 was available with a microfiber shell, instead of a nylon one, since I occasionally have shelter condensation issues with it.

Microfiber shells are constructed from a tightly woven nylon or polyester with high thread counts. The Microfiber Shell made especially for Western Mountaineering has a 400 thread per inch weave making it highly water repellent, more breathable, and lighter weight than that of coated or laminated fabrics such as Gore-tex and is a good option if you expect limited contact with water such as tent condensation. Good breathability is key in a down winter bag because a build-up of perspiration will degrade the down’s lofting power on a multi-day trip. However, if you plan on sleeping in a lot of wet snow caves, then perhaps the heavier Puma GWS shell is a better choice for you.

Western Mountaineering Puma MF Down Sleeping Bag

Western Mountaineering does not permit their dealers to discount their sleeping bags, making it virtually impossible to find a price break on them.

The Puma MF is a very significant purchase, but if you’re already into winter hiking or mountaineering, you’ve hopefully already gotten over the sticker shock of buying lots of expensive gear. I consider my Puma MF to be an excellent investment and have enjoyed using it over the years.

Disclosure: The author owns this product and purchased it using their own funds.

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  1. Why did you choose the MF vs the GWS. I m in a similar dilemma. Pls help.

    Also, a question the for the open forum. Given that I sleep cold and I use a four season tent, what Western Moutaineering sleeping bag would you suggest I buy for in winter in the cascades. Eg Mt shastha, Mt hood, Mt Rainier.

  2. It was mainly a question of availability and secondarily of price. I've found the GWS hard to find in stock, but I also don't need it since I started using a bivy more in winter. For example, I wouldn't count on the GWS alone in a snow shelter. I've never been to the Cascades – I suggest you contact a guide and ask for their advice,

  3. Do you use a bbl hot sac or equivalent when using this bag.

    Is there a real serious threat from internal moisture if the trip is only for about two days .

  4. What compression sack do you have shown here, and size?

  5. I have owned a WM Megalite (overstuffed) for the past 6 years and it has served me very well. Excellent quality.

    BUT… when I wanted a -20 F. down bag I got an LL Bean 750 fill goose down bag with Down Tec DWR treatment. THE best designed winter bag I have ever seen, and I’ve seen a lot of them.

    I got the “Bean bag” on sale but still would have paid the $419. original price B/C I felt the equivalent WM bag at over $800. was just too expensive.

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