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
| Capacity | 18 L |
| Weight | 1.3 kg |
| Dimensions | 45×25×19 cm |
| Airline fit | 96% |
| Price | $475 |
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 |
| Material | |
| Challenge Sailcloth Ecopak® EPLX600 | Available in: X-Pac X42, 500D, 630D HD |
Alpha One-Niner SERT, PENUMBRA 2.0 Backpack
| Capacity | 21 L |
| Weight | 1.5 kg |
| Dimensions | 47×30×14 cm |
| Airline fit | 93% |
| Price | $255 |
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.