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Magma Sleeping Bag Side Seam Design

How are the side seams and baffles on the Magma Sleeping Bag designed? Specifically, is the construction such that I might be able to remove the side seam opposite the zipper to allow for manual manipulation of the down fill bottom to top and back for some added temperature control? What information can you provide me relative to this experiment on my part (my risk 🙂 ). I am looking to mimic the design of the old North Face down Blue Kazoo, if you familiar with that. Thanks. SE

5 Replies

@Missoula Thanks for reaching out!

Wow, this is a tricky question and one that made us spend some time visualizing what you're hoping to achieve! It would be helpful, first, to know what you specifically like about the seam design of the Blue Kazoo - can you tell us more about that? And then we'd love to know what you're trying to achieve with your proposed modification. Are you concerned with that bag running too warm? Too cold? With that information, we can probably provide a better answer. And, with all of that said, it sounds like you recognize there is some risk associated with modifying any piece of gear. We have reached out to our design team to get some specific answers about the side seam on the Magma. We’ll get back to you with that information as soon as we are able.


At REI, we believe time outside is fundamental to a life well lived.

The original (maybe still?) NF Blue Kazoo down bag had no seam or stop preventing down movement between the top-side and bottom side of the bag. This, by design, allowed some adjustment of the fill, i.e. you could shake more of the down on top making it warmer, similar to a modern day quilt having less or nothing underneath your body. I really like sleeping bags and I really like my Magma 30’s performance. I’m wondering, however, if it would be possible push it’s warmth rating a bit by removing the side seam and having the option of stacking more down top-side. That said, it is a pretty efficient bag as is. I look forward to any information you might have regarding my proposed maybe there is a baffle at seam or some other obstacle to my plan. Thanks for your help and pondering...



@Missoula Thanks for the clarification!

We'll do our best to track down the information you need and we'll be back in touch as soon as we can. Thanks!

At REI, we believe time outside is fundamental to a life well lived.


Thanks for your patience as we tracked down the information you are looking for! We heard back from our sleeping bag designer and, while this is a very ambitious gear modification, it is possible to do. There are some things you’ll want to think about before embarking on this gear journey:

  • Your success will depend on your skill, equipment on hand, and how meticulous you want to be.
  • As you indicated, this modification is at your own risk, as attempting to alter your sleeping bag in this way would mean it would no longer fall under our satisfaction guarantee.
  • The Magma 30 sleeping bag, relatively speaking, has less down in it, so allowing the down to shift will likely create minimally insulated areas elsewhere in the sleeping bag.

All of that said, to start, turn the bag inside out, position the zipper side down and gently shake to shift the down towards the zipper side of the sleeping bag. Drape the sleeping bag over a sawhorse or the back of a couch, so half of the sleeping bag hangs on either side and gravity aids in preventing the down from escaping while you work.

The top and bottom baffles of the Magma 30 sleeping bag are divided by another baffle running nearly the length of the bag (we’ll call it the ‘L-baffle’) and an adjacent L-seam on which it anchors. In order to create a sleeping bag with continuous, traversing, top to bottom baffles, the ‘L-baffle’ needs to be removed entirely. In order to minimize escaping down, you would want to limit the length of incisions made to the bag. You could accomplish this by making 2 or 3, ~6” openings in the L-seam equally spaced along the sleeping bag. You would want to start with only one, to get your bearings, understand what you’re up against, and retreat easily if needed.

Via the opening, you can study the baffles and determine how to carefully snip away at the ‘L-baffle’ with sharp scissors. This is where you need to be meticulous, as you must be careful not to damage the traversing baffles you encounter as you move down the length of the sleeping bag. If all goes well, you can stitch closed the openings when you are finished. 

Because the traversing baffles intersect the L-baffle, it is unlikely you will get a truly ‘continuous’ baffle, connecting from the top to the bottom. Our designer said that he was fairly certain there would be a small gap present (i.e. the walls of the baffles would not connect and fall slightly short of each other).  

If you felt confident in this approach, you could make the cuts to the L-seam longer, say 1/3 of the sleeping bag at a time, in order to make it easier to see the parts of the L-baffle. However, this would require managing more loose down from the L-baffle and would be much more challenging to reverse course if things do not go well.

Hopefully this helps, best of luck!

At REI, we believe time outside is fundamental to a life well lived.

Wow! Thank you to the designer for such detail and thoughtfulness regarding method in answering my question. I must let this sink in and then will determine if I want to proceed.

Again, I appreciate REI’s due diligence. I will let you know the results if I take the “leap” on this modification.

Hike on!