Knack Pack Series 2 Review: A Clever Convertible Travel Backpack

Introduction

The Knack Pack Series 2 is designed to do two jobs at once: function as a slim daily day pack and expand into a proper travel backpack. That convertible idea is not new, but the Series 2 is the most refined execution of it yet, and it is the design that stands out most in the Knack lineup.

The version reviewed here is the medium size, which fits under an airplane seat in both unexpanded and expanded modes. That alone makes it worth a close look if you travel light and dislike checking bags.

Capacity: Slimmer Than the Label Suggests

The listed dimensions of about 19 by 12 inches are accurate for length and width, but the listed 4.5-inch depth is only realistic if you barely pack anything. In unexpanded mode with real gear inside, the bag measures closer to 6.5 to 7 inches deep, and the expansion zipper brings it to roughly 9 to 9.5 inches when fully packed.

A fill test with packing peanuts tells a more honest story. The front compartment plus main volume reached just under the 20-liter mark unexpanded, and just about 30 liters when expanded, rather than the listed figures. In practice, treat this as a roughly 19-to-30-liter convertible pack.

If you genuinely need that extra capacity, the large size is the safer pick, since the medium runs slimmer than its listed capacity suggests.

Build Quality and Materials

Knack uses a medium-weight 420 nylon with a very tight weave, which gives the bag a smooth, sleek look that matches its overall aesthetic. A PU coating adds decent water resistance, though this is not a waterproof bag.

The hardware is where the Series 2 feels solid. Large number-8 YKK zippers run the main exterior pockets, with smaller number-5 zippers on accessory pockets. The two main zippers are also lockable, so a standard travel lock or a small micro lock works well for added security.

Exterior Organization and Bottle Pocket

Instead of several small outside pockets, the Series 2 concentrates on one large front organizational compartment. Because of how the front panels are sewn, the pocket pops out slightly and has real volume of its own, with dividers in a range of sizes, stretchy divider cords, a fuzzy-lined pocket for sunglasses or a phone, a key leash hook, and a zippered mesh pocket on the lid side.

The single side water bottle pocket is deceptively large. Its capacity sits inside the pack rather than bulging outward, which keeps the silhouette sleek but takes up interior room. Skinny bottles up to nearly a liter fit fine, but wide metal bottles or a one-liter Nalgene will not fit. Around back you also get several carry handles, an external laptop compartment, a luggage pass-through sleeve with a hidden flat pocket behind it, and a secret pocket.

Carry System and Comfort

The carry system is stowable and works well in both modes. Shoulder straps are moderately wide with softer closed-cell foam inside and a breathable mesh backing. They are thinner than the thickest straps you will find on some travel packs, but more padded than those on the Peak Design travel backpack.

Straps attach with metal clips and can be removed entirely, then tucked into the top pocket for briefcase carry. The sternum strap slides easily on a rib and is removable too. Back padding is a single piece of molded foam: rigid enough to hold shape, soft enough to compress, with good ventilation channels.

One gap worth knowing about: the medium Series 2 does not include a hip belt, and the separately sold hip belt does not connect to this size. The large size does include one, and extra fabric loops like those on the large would have been a welcome addition here, since the bag can get a little heavy when expanded.

Laptop Protection

The dedicated side-access laptop compartment holds up to a 15-inch laptop. A 15.5-inch Dell fits without a problem, but anything larger likely will not. Padding is thick against the back with a thinner layer on the front, and while there is no false bottom, the back padding and zipper seam placement offer reasonable protection as long as you do not slam the bag down.

Interior: Two Compartments That Make the Design Work

The interior is where the versatility comes from. The front compartment has a top-opening zipper and carries most of the unexpanded volume, with a mesh sleeve, two larger pockets, a fuzzy-lined sleeve for a tablet or e-reader, and space enough for small packing cubes, a toiletry kit, and a light jacket. Pack light enough and this section alone covers a short weekend trip.

The real highlight is the expansion zipper, which opens a suitcase-style back compartment with a three-sided zipper that lays flat like a clamshell. Expanded, it adds nearly 10 to 11 liters for clothes and bulky items, plus a large mesh zippered pocket on the lid. Knack’s own packing cubes fit almost perfectly; standard 14-inch cubes do not work well in a 12-inch-wide bag.

The smartest packing strategy: keep clothes and items you rarely need in the back compartment. Travel expanded, unpack at the hotel, cinch it down, and you are left with an organized day pack without reorganizing anything.

Carry Comfort in Both Modes

In expanded mode, the bag carries decently. The shoulder straps are padded enough for a pack this size, and since the realistic capacity is only around 30 liters, it is hard to overload it badly. Still, if you did pack it heavy, a hip belt option would be missed.

For daily commuting in unexpanded mode, comfort is genuinely good, and the briefcase-carry option adds flexibility for shorter outings.

Buying Advice

Choose the medium Series 2 if you want a seat-compatible personal item that doubles as a day pack and you pack light. Step up to the large if you want more capacity and the included hip belt. If you already own a Series 1 and love it, the Series 2’s cleaner single-front-pocket design and sleeker silhouette are the main reasons to consider switching.

Conclusion

The Knack Pack Series 2 earns its place as a versatile, well-organized convertible travel backpack. The expansion system adds roughly 10 liters on demand, letting the bag switch between functional day pack and organized travel bag without repacking, and the tight 420 nylon build and lockable YKK zippers back that up with real quality. For one-bag travelers who value a slim profile, it is an easy recommendation.