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Outdoor Gear Lab Editor's Choice: REI Co-op Traverse 35 backpack. Confirmation of volume capacity?

I noticed recently that Outdoor Gear Lab had rated the REI Traverse 35 an Editor's Choice as the best day pack for heavy loads. This pleased me greatly because I picked one up about a year ago, planning to use it for lots of trips, but particularly for paleontological field trips, when hopefully you come back with a heavier pack that you started with, bulging with paleo goodies.

But I was surprised to note that they gave the T 35 a capacity of 48 liters, while you rate the T 35 as, at the most, 37 liter for the large size...What gives?  Is the difference the open stash pocket, a typo, or what?

I am very happy with the pack, which I purchased on sale for half price and it has served well, although I can't use it to backpack the largest specimens.  The stuff we collect ranges from trivial (stuff it in your shirt pocket) to much bigger.  The largest weighed a little over 800 pounds and I alertly decided against putting it in my wonderful Traverse 35.

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5 Replies

@hikermor Thanks for checking in with this question!

This is such a great backpack, we're always excited to receive recognition from our peers but even more so from our users in the field. If you want to send along a pic of your Traverse in action on one of your paleontological field trips we'll be happy to pass it along to the team who designed and built this pack, they'd love it!

In terms of the volume, we'll check in with our pack team to see what their thoughts are. In reading the full review by Outdoor Gear Lab it sounds like they have the volume of the main pocket at 39 liters and, by filling all of additional pockets, they were able to push that volume to 48 liters. As someone who owns this pack I also find that to be pretty generous, but as I was looking at the size of the pockets I thought that it may not be outside of the realm of possibility. We'll circle back with you here in the community when we hear back.


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

@hikermor  I have a Traverse 35 also and I'm not sure where ODGL got 48L either.  I have a Medium and the main compartment is in the 35-37L range according to my measurements...pretty much on par with what REI states.   It depends a bit on how closed the bag is for the measurement.  Possible ODGL added all the pockets.

Oddly REI give a another size measurement...M: 26x 12 x 11 inches = ~3500cu inches which is ~56L ...I have no idea what that is a measurement of since it seem unrelated to the pack...except perhaps as a guide for a shipping box...or maybe a max packed size if you want to take it on an airline.

Regardless, it is a good day/overnight/no bear can pack and carries well although I have only tried carrying about 20lbs with it.  It has a couple of flaws... the sternum strap sliders are too loose...the wrong size filler cord was used I think...not sure if that was just a batch problem...and the padding on the hip belt padding could come further forward on the hips for better effect...the pads seem an unnecessarily economical length given their somewhat technical construction.


A  further note on this,  referencing a previous is what I managed to stuff in mine...

I said I had a Large but I was mistaken and actually mine is a Medium.




@hikermor and @OldGuyot - We have tracked down some more information for you all!

It looks like the 48 liter size describes the maximum volume of the pack, while the 35 liter name comes from what REI considers the actual useable volume. When pushed to their limit, top-loading packs have the ability to be quite overloaded, which is the main factor in this max vs useable volume difference. 

The volume in a pack's name is also derived from its most common size (medium for men's packs and small for women's), though capacity does slightly change based on which size you have. REI's measurement for max volume on the men's large is 46.5 liters, which isn't too far off from Outdoor Gear Lab's measurement. 

Thanks again for bringing this question to us! Was a fun one to get to the bottom of!

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

@hikermor @OldGuyot 

I wanted to add a couple more details to @REI-CarterC's response:

  • The gear lab at REI uses the ASTM (American Society of Test Methods) F2153 - Standard Test Method for Measurement of Backpack Capacity. Take a look at more info here.
  • That test specifically 'does not take into consideration areas of the backpack that are not completely enclosed by fabric such as mesh pockets, water bottle holders, and compressor pockets.'
  • The process for measuring volume in a pack in this way is to pack the backpack with 20mm plastic non-compressible spheres, then pour them out and measure the volume of spheres. 20mm is about half the size of a ping pong ball, for reference.

This was a really interesting journey into the details of how pack volume and naming come in to play. Thanks for the great discussion!

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