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Anyone hunting for an ultralight backpack in today’s market faces a sea of indistinguishable, crinkled, grayish-black rucksacks. The number of thru-hiker-focused designs from both cottage brands and larger companies, clad in either Dyneema or Ultra fabrics, is staggering. And while you don’t need a pack made with space-age fabrics to go ultralight, there’s no denying the appeal of a (mostly) waterproof, nearly weightless, super-durable backpack.
The two hottest contenders in the category right now are the Zpacks Arc Haul Ultra (available in 40, 50, and 60 liters) and Durston Gear’s Kakwa (available in 40 and 55 liters). Both are made from Ultra, an UHMWPE (Ultra High Molecular Weight Polyethylene) fabric that’s become the dominant ultralight pack material in the last few years. The Kakwa 55 and Arc Haul Ultra 60L have almost the same exact total volume. Both have the same basic roll-top design with a large stuff-it pocket and two side pockets. But the Zpacks is nearly twice the cost.
I took both packs out on Vermont’s Long Trail for two, week-long backpacking trips to answer the question: which of these two ultra-popular, ultra-similar ultralight backpacks deserves your money?
Zpacks Arc Haul Ultra 60L ($399)
Weight
Let’s get straight to it: the Arc Haul Ultra is light as hell. With additional hip and phone pockets, my 60-liter pack came in at roughly 1 pound, 7 ounces. That’s thanks primarily to very lightweight Ultra 100x fabric (3.3 ounces per square yard) and carbon fiber stays. Ultra 100x is plenty durable for the daily rigors of thru-hiking or backpacking: I wasn’t able to cause any damage by scooting across sharp rock or busting through brambles while bushwhacking, but the fabric does feel thin. I probably wouldn’t take it on a canyoneering trip.
As far as I know, this is the lightest 60-liter backpack you can buy without going frameless. (For reference, most ultralight packs of this volume are around two pound range.) For serious gram-counters, this alone might sway you towards the Arc Haul over another pack.
Features
One of the major drawbacks to the Arc Haul is that it comes without hipbelt pockets. Zpacks has an extensive accessory shop where you can buy zippered hipbelt pockets ($33 each), zippered shoulder pouches for phones and cameras ($43), and water bottle sleeves ($30) just to name a few. It’s a tinkerer’s dream, albeit a costly one. Assuming you want two hipbelt pockets and a phone pouch, you’re looking at a $508 backpack.
Beyond the lack of included pockets and pouches, the Arc Haul has a fairly standard ultralight pack feature set, with a large, 8-liter mesh front pocket, two 2.5-liter slanted side pockets, bungee straps on either side, and a roll-top closure. It’s important to note that all the seams and attachment points are taped, which makes this pack extremely water-resistant. It held up to hours-long summer thunderstorms without so much as a drop of leakage, and would probably keep your stuff safe on an impromptu paddling trip, as well.
Comfort
Comfort is where the Arc Haul really shines. This pack allows you to adjust the positioning of the shoulder strap’s top attachment point, which I think should be a feature on every backpack. By loosening an extra tab, you can drop the anchor point of the straps into the perfect trapezius-hugging position, which makes dialing in the fit and geometry of your load-lifters super-precise and allows the shoulder straps to lay in the ideal position across your body.
Another “luxury” design perk is the Arc Haul’s trampoline Lycra mesh back panel, which keeps the back of the pack material from sticking to you when you sweat. While this system doesn’t work as well as more complicated, substantial designs from big, non-ultralight brands like Osprey and Deuter, it allowed for some much-needed airflow around the lower back. (The upper back still makes contact in spite of the mesh.)
The hipbelt and shoulder straps are padded with foam and wrapped in a 3D spacer mesh, which felt adequate—not too spare as to create chafing or soreness, but not so luxurious that you want to keep your pack on during snack breaks.
Carry-Capacity
The ability to carry relatively heavy loads (35 to 40 pounds) during long stretches between resupplies or extended water carries is critical for any thru-hiker. To that end, I loaded the pack up with 40 pounds of weight (Zpacks’ claimed capacity) for a 14-mile hike along Vermont’s Long Trail. The Arc Haul’s suspension system, which is essentially a flat, carbon-fiber ladder that’s arched slightly to allow for airflow, is an excellent design. Its rigidity and structure is on-par with much more robust, heavyweight designs from non-ultralight brands.
The Arc Haul has a pass-through, rather than sewn-in hipbelt, meaning it can be removed if you want to strip your pack down for weight savings. That pass-through design also means the pack pivots slightly as you walk. I found the flexibility felt great and ultimately saved energy while walking for long, mostly-flat stretches, but it was a bit unwieldy when scrambling or tilting to one side while climbing over logs
With a load of 40 pounds, I also found the pack sagged slightly, concentrating the bulk of the load toward the tailbone instead of distributing it more broadly across the waist. That led to some soreness at the end of the trip. Zpacks makes a lumbar pad accessory that fixed the pressure point completely, but adds $25 to your total bill. If you’ll be carrying more than 30 pounds, though, I’d say it’s a worthy upgrade.
Durston Kakwa 55 ($260 in Ultra 200x)
Weight
The Kakwa 55 hit the scales exactly at its advertised 1 pound, 14 ounces, which is quite good for a framed ultralight backpack of its size, even if it can’t match the Arc Haul’s welterweight status. The premium version of this pack uses Ultra 200x, which is, as you might expect, a good deal more durable than the 100x on the Arc Haul. I abused this pack fabric while squeezing through boulders and bushwacking through scrubby Vermont wetland and haven’t seen a single pinhole. For a frame, Durston uses a hollow, 3-ounce aluminum tube shaped into an inverted “U.”
Features
Durston Gear owner Dan Durston has a bit of a cult following for his tent designs (we gave his X-Mid an Editor’s Choice award in 2024), and there’s a good reason: the man walks his talk, offering layouts and features only a longtime backpacker would dream up. The Kakwa is no different. Two large zippered pockets on the hipbelt are each big enough for a smartphone, and stretchy, running vest-style polyester mesh pockets are perfect for bear spray, small water bottles, or a satellite messenger. The front shove-it pocket, made of an especially durable knit mesh, is smaller than the one on the Arc Haul, but it’s still large enough to stash rain shells or a fleece on the fly.
The side pockets are a simple, thru-hiker-tailored design: one slants forward for easy water bottle access, while the other is deep and straight for tents, poles, or sun umbrellas. The deeper side pocket has a full-length vertical zip for easy access to bulky apparel. I found myself jamming a rain poncho in there, which I was able to quickly deploy during sudden rainstorms without taking my pack off.
The Kakwa 55 is very water resistant, but not seam-taped, so it’s technically more susceptible to leakage than the Arc Haul. I never had any water seep in during hours-long downpours, but it could be an issue if you left it outside your tent during an overnight storm. With time and patience, you could technically seam-seal the pack yourself.
Comfort
The Kakwa’s S-shaped shoulder straps and foam padding are nearly identical to the design on the Arc Haul and offer the same, moderate level of cushioning. Ultra 200x fabric makes for an especially sticky, impermeable material against the back, however, and I missed the Haul’s breathable mesh back panel, especially on humid New England days. Most thru-hikers quickly become acclimated to the sweaty discomfort associated with minimal ultralight packs, but more casual backpackers might be bothered.
My biggest gripe with the Kakwa is the design of its hipbelt buckle. Durston swapped out the typical buckle design with a new one that features clip “wings” that stick out prominently, intended to make it easier to use when you’ve got cold, numb hands. Unfortunately, this new buckle dug into my skin when cinched all the way down under a 40-pound load. I also found that it unbuckled itself when I bent over to tie my shoes. According to Durston, the brand will be reverting back to the original design later in 2024 for exactly those reasons. For now, if you’re set on a Kakwa and find the buckle to be problematic, we’d recommend swapping it out for a standard-issue style or waiting for the updated version.
Carry Capacity
Durston says its Kakwa can carry 45 pounds comfortably, which is a bold claim for any ultralight pack. The aluminum frame does a great job of distributing weight to the hipbelt. Credit the construction: the frame stays extend all the way down through the hipbelt, and that the hipbelt is sewn directly to the pack. Overall it makes for a stiffer, less dynamic experience than I had with the Arc Haul’s more flexible, removable belt. Loaded with 40 pounds, I wouldn’t exactly call the Kakwa’s carry experience comfortable; it required lots of micro-adjustments to keep the weight from slowly slipping back onto my shoulders as I hiked. While you could probably carry 45 pounds without pack failure or injury, I wouldn’t want to hike with much more than 35 pounds for an extended period.
So Which Pack is Better?
There’s no simple answer. Both packs are well-designed and have exceptional carry capacities for their volume.
The Arc Haul 60 is a more comfortable pack to wear over long periods, especially with a heavy load. Its mesh back panel, adjustable shoulder straps, sturdy carbon frame, and flexible hipbelt make for a winning combination that’s hard to beat. Its base weight is impressively low, and for serious gram-counters, that will be a major deciding factor. For those without budget restrictions, Zpacks’ deep stock of accessory pockets and pads means you can have a fully customized kit.
But for most thru-hikers and ultralight backpackers, the Kakwa 55 wins out with its very modest $260 price point, clever pocket design, and durability. (The hopefully temporary buckle issue notwithstanding.) If spending $400 to 600 on a pack doesn’t feel outrageous to you, however, Zpacks’ Arc Haul is still the Cadillac of ultralight packs.
Note: While Zpacks and Durston Gear are the ultralight cool kids, there are many, many ultralight packs out there. For a wide-ranging comparison of the ultralight pack market, stay tuned for the 2025 summer gear guide, launching next spring.