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If you're the dude who cuts his toothbrush in half, shaves his legs, and pulls out all his teeth to save weight before going backpacking, odds are you'll fall in love with the Marmot Plasma 40-Degree Down Sleeping Bag. It's pretty much a one-season bag (mild spring and fall nights will be OK, too), but good gravy, is it light and packable—does 1lb 2oz float your boat? The Plasma's able to be so minimal because it packs super-high loft 875-fill down into a Pertex Quantum shell, which is extremely durable but still light as a feather, and uses Insotect Flow vertical baffles to direct heat to your extremities. In that way it keeps your feet warm without the need for more down, which would just take up space in your pack.

If it's not enough that the Plasma would pack into your water bottle, its down is treated with Down Defender to improve its water-resistance, and the bag's exterior has a DWR coating to shed water and keep the insulation functioning with optimum efficiency. It also has a litany of desirable features, like an insulated draft tube and collar, two-way zippers with garages, and a soft face muff to seal out drafts around your mug. Hang it up using the loops, store it in a loose sack to keep the down lofted, and you'll have ultralight summer insulation for years.

  • 40-degree rating
  • 875-fill down with Down Defender water-resistant treatment
  • Mummy bag with Insotect Flow vertical baffles
  • 10D Pertex Quantum nylon ripstop fabric
  • Ultralight
  • Drawcord hood with insulated collar and draft tube
  • Wrap-around footbox construction
  • Two-way zippers with garage
  • Hang loops
  • Reviews
  • Q & A

What do you think about this product?

Have questions about this product?

Warm and Packable

  • Familiarity: I've put it through the wringer

This is a great little bag for folks looking for something that won't take up half the space in your pack. For summertime backpacking or climbing trips, this bag is more than enough if you plan to sleep in your clothes. I took this on a 10 day section of the John Muir Trail and had no issues sleeping in this bag at 10,000 plus feet. The bag will pack down smaller than a coffee can if you get a good stuff sack. I'm 6'3" and the regular length worked fine. Weighs about a pound and a quarter.

I would like to know about to waterproof performance.

The bag uses Down Defender meaning that the bag will be a little more resistant to water and dry faster should it get wet. By no means will you be warm or comfortable if the bag gets soaked, it just means it will do better than a straight up down bag without the Down Defender. The Down Defender is a back up to taking care of your bag and ensuring that it stays dry.

You can call or email me directly. 801-736-6398, or

Hey Kyungwon,

I have this sleeping bag and by no means is it waterproof and waterresistance.

I wouldn't put any value on the Down Defender. While the down is treated, I wouldn't rely on that. Otherwise you'll be setting youself up for a bad time.

Shoot me an email anytime you have questions!

Jared D.

Expert Gearhead