Description
The traveler this Subterra convertible suits
This is a 40 liter soft carry on with no wheels that converts between a shoulder bag and a backpack, has a suitcase style opening, and carries a removable laptop sleeve. It is aimed at the traveler who moves between offices and airports and wants one bag for both, and at the person who has decided that on their routes carrying is faster than rolling.
Three and a half pounds empty is the number that defines it. A wheeled bag of the same volume in this catalog weighs seven or eight pounds, and every pound of empty bag is a pound of contents you can carry within the same allowance. The trade is your shoulders: 40 liters packed weighs 20 to 30 pounds and you carry all of it. If your route is long terminal walks, stairs and public transport, that is a good trade. If it is standing in lines with a full load, it is not, and the wheeled options in our carry-on luggage section are the answer instead.
Dimensions, and a bag that fits the guideline
Thule publishes 8.3 by 13.8 by 21.7 inches, and the figure appears twice on the listing, in the specification block and in a feature bullet, with the same numbers both times. Agreement between two independent fields is unusual on this catalog and worth noting.
Set against the size guideline most commonly cited for United States domestic cabin baggage, roughly 22 by 14 by 9 inches, this bag is inside on all three axes: 21.7 against 22, 13.8 against 14, and 8.3 against 9. That is a bag designed to the number rather than rounded toward it, and it is the rarest outcome in this whole category.
What still needs checking
Two things. First, a soft bag with no frame measures differently depending on how it is packed. Empty it is under the published figures; stuffed to 40 liters with hard objects it can bulge past them, particularly on the depth axis. Second, the shoulder straps and the removable strap add depth when they are not stowed. Tuck or remove them before you approach a gate.
We will not write that this bag is airline approved and Thule does not claim it. Check the allowance published by the carrier and fare you booked, note that budget and regional carriers publish smaller allowances than the majors, and remember that many international carriers weigh cabin baggage as well. At 3.5 pounds empty this bag is unusually well placed for the last of those.
Fabric, construction and the conversion
The body is 800 denier nylon, and the listing publishes the denier rating in both the material field and a feature bullet. That is the disclosure this whole category usually withholds, and it lets you judge the fabric properly. Eight hundred denier nylon is a substantial weave: heavier and more abrasion resistant than the 600 denier polyester used on mid range bags, lighter and less bulletproof than a 1680 denier Oxford or a ballistic nylon. Thule also calls it water resistant, which means a treated surface that sheds a shower. It is not waterproof, and on any zippered bag the zipper line is where water gets in.
The conversion between shoulder bag and backpack is the defining feature. Two carry modes on one bag sounds like a compromise and often is, because a shoulder strap arrangement that tucks away rarely carries as well as a dedicated harness. What makes it work here is that 40 liters at 3.5 pounds empty is a load light enough that a simple harness is adequate; the same conversion on a 60 liter pack would not be.
The suitcase style opening is the other reason to buy this over a conventional duffel or top loading pack. The bag lies flat and opens fully, so you see everything at once instead of digging, and a zippered mesh divider gives the flat opening some structure. A multi purpose compartment keeps shoes or laundry away from clean clothes, which is the single most useful piece of organization in any travel bag.
The laptop sleeve is removable and rated for a 15 inch MacBook, a 15.6 inch PC, a 10.1 inch tablet and accessories. Removable matters: attach the strap to the sleeve alone and you have a slim bag for a meeting, leaving the main bag at the hotel. That is a genuinely useful two in one rather than a gimmick.
Other details: an integrated pass through panel slides the bag over the handle of a rolling case, so it works as the second piece in a two bag system, and a hidden pocket that Thule calls CashStash takes a passport and documents. Understand what a hidden pocket buys you. It defeats a casual hand in a crowd. It defeats nothing else, and it is not a substitute for keeping documents on your person in a genuinely risky setting.
Capacity, weight and what a bag with no wheels gives up
Forty liters is published in the size field, the capacity field and a feature bullet, all in agreement. Against an envelope of roughly 2,380 cubic inches, or about 39 liters, the 40 liter figure is right at the exterior envelope, which is normal and correct for a soft bag with no shell thickness, no handle channel and no wheel wells to subtract. Compare that with a wheeled hard case, which typically loses a quarter of its envelope to structure.
That is the real efficiency argument for a wheelless bag and it is worth stating numerically. This bag holds 40 liters in an envelope where a wheeled case of the same external dimensions would hold around 30. You gain a third more usable space and you lose the wheels.
Three and a half pounds empty is the standout figure. It is less than half the empty weight of the wheeled cases of comparable volume in this catalog. On carriers that weigh cabin baggage against a 7 or 8 kilogram allowance, that difference is roughly four pounds of clothes you get to bring that a wheeled traveler does not.
What you give up, beyond the obvious, is protection. A soft bag with no frame offers nothing against being crushed under a heavy case in an overhead bin. If you carry breakables, a structured bag such as the Thule Crossover 2 carry on spinner, which has a dedicated crush resistant compartment, is the better tool.
Warranty and the alternatives
The warranty description field on this listing reads, in full, manufacturer defects. That is not a warranty statement so much as a category. There is no term, no period, no claims process, and no statement about what is excluded. In particular there is nothing about airline handling damage, which is the standard exclusion across luggage warranties and the damage that actually occurs. On a bag with no wheels there is at least less to break, but zippers, straps and stitching all fail eventually. Get the written coverage terms before ordering.
The review base is 4.6 from 323 ratings, and the model year on the listing is 2017, so this is an established design with several years of buyers behind it rather than a new product with a small sample. That combination is more useful than a high rating on a recent listing.
For alternatives, the Cotopaxi Allpa 35L travel pack is a dedicated backpack with a hip belt that carries heavier loads better, and the Osprey Farpoint wheeled travel pack adds wheels back for people who want both. The category is collected in our backpacks section.
Who should buy it and who should not
Buy it if you want maximum usable volume in the smallest cabin footprint, you would rather carry than roll, and the removable laptop sleeve fits how you work. Published dimensions inside the common guideline on all three axes, 800 denier nylon with the rating actually stated, and 3.5 pounds empty are three things almost nothing else in this catalog offers together. Skip it if you have a bad back or a long standing wait ahead of you, and skip it if you carry anything fragile, because there is no crush protection at all.
