Knack Pack Series 1 vs Series 2: Which Expandable Travel Backpack Fits Your Style?

Introduction

Knack’s expandable travel packs are built around a simple idea: a front compartment that works like an everyday daypack, plus a rear expansion zone that pops out when you need serious luggage space. The Series 1 and Series 2 share that same underlying design, so the real question is not which design is better, but which execution suits you. This comparison looks at capacity, materials, pocket layout, and how each version actually packs.

Capacity: Measured, Not Just Listed

Both bags expand from roughly the same unexpanded size, about 19 to 20 liters. The Series 2 measures around 20 liters unexpanded and about 30 liters expanded. The Series 1 is listed at 27 to 39 liters, but a packing-peanut capacity test suggests it lands closer to 32 to 33 liters expanded, roughly two to three liters more than the Series 2.

In unexpanded mode, both fit inside an 18 by 14 by 8 inch personal item sizer box, which makes either pack a viable personal item on many budget airlines. Expanded, they are generally too big for the sizer and would need to go in the overhead bin.

Fabric and Build Quality

The exterior fabrics are completely different. The Series 1 uses a thicker, softer polyester with a heathered look. The Series 2 goes for a sleeker aesthetic with a smoother, lighter weight nylon in a very tight weave. Neither is inherently better: both carry a durable water resistant coating, so it comes down to personal style preference.

The hardware is nearly identical across both versions. Both use large YKK zippers, including locking zippers on the two main compartments, plus Duraflex buckles. The Series 2 has slightly rounder adjusters and sternum strap clips, part of its updated look.

Front Pocket Layout: Three Pockets vs One

The most obvious design change is how the two handle small gear organization. The Series 1 splits it across three smaller pockets: top, front, and bottom. The top pocket has a fuzzy lining for sunglasses, the front pocket is a double-zip compartment with its own volume that can hold a light jacket plus document-style sleeves, and the bottom pocket is a general organizer that is a bit small for men’s size 11 shoes. Being on the bottom, it is not the place for anything fragile.

The Series 2 consolidates everything into one large front compartment with roughly the same combined volume and similar internal organization, including a fuzzy-lined top area and a mesh zipper pocket on the lid. It looks cleaner, but some people will prefer the Series 1’s separation of items.

Water Bottle Pockets

Both packs use side-access bottle pockets that add volume inside the bag rather than sticking out externally. The Series 1 has a longer zipper, so the bottle sits more in the middle of the bag; the Series 2’s pocket capacity sits toward the bottom. Slim, tall bottles fit easily in either. Larger one-liter Nalgene-style bottles fit in the Series 1 but you cannot fully close the zipper over them in the Series 2’s pocket shape.

Carry System and Strap Storage

The carry systems are virtually identical: same back padding, same straps and adjusters. The Series 1 shoulder straps look slightly wider, but not enough to matter. The main difference is strap storage: both detach with small metal lobster claw buckles, but the Series 2 tucks each strap into its own zippered pocket for a sleeker profile, while the Series 1 folds them behind the back padding under a simple fabric flap.

The laptop compartment is essentially unchanged on both: a large side-access zipper with good padding at the back and front, and no false bottom, though the back padding curves around the bottom for extra protection. Note that newer Series 1 units route the luggage passthrough through the side, matching the Series 2, rather than from the bottom as on earlier units.

Interior Organization and Expansion

The front compartments open differently. The Series 1 opens flat-panel style with most volume behind the zipper, while the Series 2’s zipper sits more centrally, so the front compartment opens more like a school backpack with volume in front of the zipper. Inside, both include a fuzzy-lined mesh sleeve for a tablet; the Series 1 adds two mesh zippers and a key leash, the Series 2 a mesh sleeve, one fabric zippered pocket, and one more zippered pocket. The front compartment is large enough that, packed light, it could serve as your only bag for a short weekend trip.

The expansion zipper runs around the back of both packs and pops out a clamshell-style compartment that works like a giant packing cube, adding 10 to 12 liters. Each has a big mesh zipper on the lid and a compression strap in the middle. Packing cubes around 12 inches wide or narrower fit; 14-inch cubes are too wide. The recommended approach: day gear in the two front compartments and water bottle, clothes and bulky items in the rear section, then once you arrive, compress the expansion away and your daypack is already organized.

Series 1: The Roomier Classic

The Series 1 stands out for capacity, holding roughly two to three liters more in expanded mode, and for its softer heathered polyester look. Its three separate front organizer pockets let you separate documents, tech, and other gear. It also fits larger water bottles more comfortably. The trade-off is a less streamlined exterior and a simpler strap-stow system without dedicated zippered pockets.

Series 2: The Sleeker Update

The Series 2 keeps the same core design but delivers a sleeker, more modern aesthetic with its smooth tight-weave nylon and consolidated single front organizer pocket. Strap storage is tidier with individual zippered pockets, and the overall profile is cleaner. The trade-offs are slightly less expanded capacity and bottle pockets that cannot close over oversized bottles.

Buying Advice

Neither pack is a clear upgrade over the other; the changes are largely aesthetic plus the reworked front pocket organization. If you want maximum expandable capacity and prefer separate organizer pockets and a softer textured fabric, the Series 1 is the stronger fit. If you value a sleeker look, consolidated organization, and tidy strap stowage, choose the Series 2. One thing worth appreciating: Knack kept both versions in the lineup, and the Series 1 is now offered in updated colors rather than being discontinued.

Conclusion

The Series 1 and Series 2 are the same good travel backpack at heart, with the Series 2 offering a sleeker exterior and consolidated organization while the Series 1 offers a bit more capacity and a three-pocket front layout. Measure your priorities, style or space, and either one should serve you well as a personal-item-sized travel pack.