---
url: "https://onebag.travel/compare/ahyvuk1jes/attitude-supply-atd2-backpack/ayd517mvmi/alpha-one-niner-sert-penumbra-2-0-backpack/"
title: "Attitude Supply ATD2 Backpack vs Alpha One-Niner SERT, PENUMBRA 2.0 Backpack"
description: "Attitude Supply ATD2 Backpack vs Alpha One-Niner SERT, PENUMBRA 2.0 Backpack: capacity, weight, dimensions and how many airlines accept each as a carry-on…"
source: "https://onebag.travel/compare/ahyvuk1jes/attitude-supply-atd2-backpack/ayd517mvmi/alpha-one-niner-sert-penumbra-2-0-backpack/"
---
1.  [Home](https://onebag.travel/)
2.  [Carry-On Travel Backpacks](https://onebag.travel/carryons/)
3.  Attitude Supply ATD2 Backpack vs. Alpha One-Niner SERT, PENUMBRA 2.0 Backpack

# Attitude Supply ATD2 Backpack vs. Alpha One-Niner SERT, PENUMBRA 2.0 Backpack

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

## [Attitude Supply ATD2 Backpack](https://onebag.travel/carryon/ahyvuk1jes/attitude-supply-atd2-backpack/)

by [Attitude Supply](https://onebag.travel/carryons/?brands=Attitude Supply)

![Front facing view of the Attitude Supply ATD2 Backpack](https://res.cloudinary.com/obt/image/upload/c_fill,w_400/v1788990291/carryons/attitude-supply-atd2-backpack-ahyvuk1jes.webp)

<table class="table table-sm cmp-spec mt-2"><tbody><tr><td>Capacity</td><td>18 L</td></tr><tr><td>Weight</td><td>1.3 kg</td></tr><tr><td>Dimensions</td><td>45×25×19 cm</td></tr><tr><td>Airline fit</td><td>96%</td></tr><tr><td>Price</td><td>$475</td></tr></tbody></table>

## Feature by feature

| Attitude Supply ATD2 Backpack | Feature | Alpha One-Niner SERT, PENUMBRA 2.0 Backpack |
| --- | --- | --- |
| Storage |
| 4 | Compression | 2 |
| 31L | Expanded Capacity | None |
| 1 | Opening | 1 |
| front | Passport | front |
| Y | Passthrough | Y |
| Carry |
| removable | Backpack | Y |
| removable | Hip Belt | optional |
| removable | Sternum Strap | removable |
| Inside |
| 15in | Laptop | 16in |
| 2 | Main Compartments | 5 |
| Y | Organizer | Y |
| Outside |
| × | Hard Shell | × |
| N | Rain-fly | N |
| 2, side | Water Bottle Holder | 2, side |
| Y | Water Resistant | Y |

<table class="cmp-material"><tbody><tr><td colspan="2">Material</td></tr><tr><td>Challenge Sailcloth Ecopak® EPLX600</td><td>Available in: X-Pac X42, 500D, 630D HD</td></tr></tbody></table>

## [Alpha One-Niner SERT, PENUMBRA 2.0 Backpack](https://onebag.travel/carryon/ayd517mvmi/alpha-one-niner-sert-penumbra-2-0-backpack/)

by [Alpha One-Niner](https://onebag.travel/carryons/?brands=Alpha One-Niner)

![Front facing view of the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack](https://res.cloudinary.com/obt/image/upload/c_fill,w_400/v1788990332/carryons/alpha-one-niner-sert-penumbra-2-0-backpack-ayd517mvmi.webp)

<table class="table table-sm cmp-spec mt-2"><tbody><tr><td>Capacity</td><td>21 L</td></tr><tr><td>Weight</td><td>1.5 kg</td></tr><tr><td>Dimensions</td><td>47×30×14 cm</td></tr><tr><td>Airline fit</td><td>93%</td></tr><tr><td>Price</td><td>$255</td></tr></tbody></table>

## Key differences between the Attitude Supply ATD2 Backpack and Alpha One-Niner SERT, PENUMBRA 2.0 Backpack

-   **Compression straps:** 4 on the Attitude Supply ATD2 Backpack; 2 on the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.
-   **Backpack straps:** Removable on the Attitude Supply ATD2 Backpack; Yes on the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.
-   **Hip belt:** Removable on the Attitude Supply ATD2 Backpack; Optional on the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.
-   **Laptop sleeve:** 15in on the Attitude Supply ATD2 Backpack; 16in on the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.
-   **Main compartments:** 2 on the Attitude Supply ATD2 Backpack; 5 on the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.

Both have: passport pocket, luggage passthrough, sternum strap, built-in organizer, water bottle pockets, water resistant.

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

We checked both bags against the carry-on size limits of 189 airlines. 175 accept both. 6 accept only the Attitude Supply ATD2 Backpack, and 0 accept only the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack.

### Only the Attitude Supply ATD2 Backpack fits

Air Tahiti, American Eagle, easyJet, Great Lakes Airlines, Gulf Air, Ravn Alaska.

## Attitude Supply ATD2 Backpack vs. Alpha One-Niner SERT, PENUMBRA 2.0 Backpack: which should you pack?

The **Alpha One-Niner SERT, PENUMBRA 2.0 Backpack** carries 3L more than the **Attitude Supply ATD2 Backpack** (18L vs. 21L), while the **Attitude Supply ATD2 Backpack** is the lighter pack at 1.3kg (vs. 1.5kg). For carry-on flexibility, the **Attitude Supply ATD2 Backpack** fits 96% of the airlines we track — the higher of the two. If you prioritise packing volume, choose the Alpha One-Niner SERT, PENUMBRA 2.0 Backpack; if you want to travel lighter, the Attitude Supply ATD2 Backpack is the better call.