---
url: "https://onebag.travel/compare/i3dfh43ew9/tom-bihn-brain-bag/yshyt43faw/rei-co-op-trail-40/"
title: "Tom Bihn Brain Bag vs REI Co-op Trail 40 - One Bag Travel"
description: "Tom Bihn Brain Bag vs REI Co-op Trail 40: capacity, weight, dimensions and how many airlines accept each as a carry-on, side by side."
source: "https://onebag.travel/compare/i3dfh43ew9/tom-bihn-brain-bag/yshyt43faw/rei-co-op-trail-40/"
---
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3.  Tom Bihn Brain Bag vs. REI Co-op Trail 40

# Tom Bihn Brain Bag vs. REI Co-op Trail 40

Two carry-on travel backpacks, compared spec for spec.

## [Tom Bihn Brain Bag](https://onebag.travel/carryon/i3dfh43ew9/tom-bihn-brain-bag/)

by [Tom Bihn](https://onebag.travel/carryons/?brands=Tom Bihn)

![Front facing view of the Tom Bihn Brain Bag](https://res.cloudinary.com/obt/image/upload/c_fill,w_400/v1601123264/carryons/tombrainbag_ts952i.webp)

<table class="table table-sm cmp-spec mt-2"><tbody><tr><td>Capacity</td><td>36 L</td></tr><tr><td>Weight</td><td>1.3 kg</td></tr><tr><td>Dimensions</td><td>46×36×23 cm</td></tr><tr><td>Airline fit</td><td>66%</td></tr><tr><td>Price</td><td>$240</td></tr></tbody></table>

## Feature by feature

| Tom Bihn Brain Bag | Feature | REI Co-op Trail 40 |
| --- | --- | --- |
| Storage |
| 4 | Compression | 4 |
| None | Expanded Capacity | None |
| 4 | Opening | 1 |
| top | Passport | top |
| N | Passthrough | N |
| Carry |
| Y | Backpack | Y |
| removable | Hip Belt | Y |
| removable | Sternum Strap | removable |
| Inside |
| N | Laptop | N |
| 6 | Main Compartments | 5 |
| Y | Organizer | Y |
| Outside |
| × | Hard Shell | × |
| N | Rain-fly | Y |
| 1, side | Water Bottle Holder | 2, side |
| Y | Water Resistant | Y |

<table class="cmp-material"><tbody><tr><td colspan="2">Material</td></tr><tr><td>525 Ballistic Nylon</td><td>210-denier ripstop nylon</td></tr></tbody></table>

## [REI Co-op Trail 40](https://onebag.travel/carryon/yshyt43faw/rei-co-op-trail-40/)

by [REI Co-op](https://onebag.travel/carryons/?brands=REI Co-op)

<table class="table table-sm cmp-spec mt-2"><tbody><tr><td>Capacity</td><td>40 L</td></tr><tr><td>Weight</td><td>1.2 kg</td></tr><tr><td>Dimensions</td><td>56×30×23 cm</td></tr><tr><td>Airline fit</td><td>47%</td></tr><tr><td>Price</td><td>$130</td></tr></tbody></table>

## Key differences between the Tom Bihn Brain Bag and REI Co-op Trail 40

-   **Opening:** Top zip on the Tom Bihn Brain Bag; Clamshell on the REI Co-op Trail 40.
-   **Hip belt:** Removable on the Tom Bihn Brain Bag; Yes on the REI Co-op Trail 40.
-   **Main compartments:** 6 on the Tom Bihn Brain Bag; 5 on the REI Co-op Trail 40.
-   **Rain cover:** No on the Tom Bihn Brain Bag; Yes on the REI Co-op Trail 40.
-   **Water bottle pockets:** 1, side on the Tom Bihn Brain Bag; 2, side on the REI Co-op Trail 40.

Both have: compression straps, passport pocket, backpack straps, sternum strap, built-in organizer, water resistant.

## Which airlines take each bag as a carry-on

We checked both bags against the carry-on size limits of 189 airlines. 87 accept both. 38 accept only the Tom Bihn Brain Bag, and 1 accept only the REI Co-op Trail 40.

### Only the Tom Bihn Brain Bag fits

Aer Lingus, Aeroflot, Aeromexico, Air Canada, Air Caraibes, All Nipon Airways, ANA, Austrian, Azerbaijan Airlines, Brussels Airlines, Czech Airlines, Ethiopian Airlines, Etihad Airways, Eurowings, Fiji Airways, Flair Air, Gol Linhas Aereas, Iberia, Interjet, Iran Air, Japan Airlines, LOT Polish, Lufthansa, Mahan Air, Mesa Airlines, Norwegian, Oman Air, Peach, Porter Airlines, Qatar Airways, Ravn Alaska, Royal Jordanian, SAS Scandinavian, Scoot, Swiss Int'l Air Lines, Tiger Airways, Turkish Airlines, WestJet.

### Only the REI Co-op Trail 40 fits

Cayman Airways.

## Tom Bihn Brain Bag vs. REI Co-op Trail 40: which should you pack?

The **REI Co-op Trail 40** carries 4L more than the **Tom Bihn Brain Bag** (36L vs. 40L), while the **REI Co-op Trail 40** is the lighter pack at 1.2kg (vs. 1.3kg). For carry-on flexibility, the **Tom Bihn Brain Bag** fits 66% of the airlines we track — the higher of the two. If you prioritise packing volume, choose the REI Co-op Trail 40; if you want to travel lighter, the REI Co-op Trail 40 is the better call.