Arc’teryx Gave Us Exclusive Access to Their Freakishly Light New Pack. So We Took It to the Mountains.

Advances in climbing equipment generally come slowly. As functionality is refined and then streamlined, designers often linger on reiterated projects, changing a color scheme here, removing a buckle there. It’s only when new materials are brought into the fold—like sticky rubber to rock shoes—that climbing equipment truly leaps forward. And that could be the case with Aluula’s “Graflyte” a blindingly white new fabric that might be alpinism’s next big thing.

Graflyte is an extremely durable, light, and waterproof fabric comprised of UHMWPE (a widely used material best known by the brand name Dyneema) with a twist: the fabric can be laminated together, thus eliminating failure-prone seams and glue and prolonging the lifespan of the product. Graflyte is also the central fabric in Arc’teryx’s latest feathery alpine pack, the Alpha SL, the 30-liter version of which weighs just 438 grams (15.2oz).

Climbing was sent a 30-liter Alpha SL earlier this year. We took it up pristine alpine granite above Squamish, B.C., toured around Colorado with it, and then went back up to Canada for a bout with the Bugaboos in mixed conditions. Our testers were unanimously psyched; appreciating the Alpha SL’s eye for simplicity, sleek features, and freakishly light weight.

How does “Graflyte” work?

Graflyte is comprised of ultra-high-molecular-weight polyethylene fibers (UHMWPE) a material whose strength-to-weight ratio is famously up to eight times greater than steel. But the neat thing about Graflyte is it doesn’t require a ton of sewing or gluing to assemble. Both of these adherent processes are by far the weak point of any UHMWPE pack. Seams tear and glue dries out. And since Aluula’s fabrics are self-adherent, they should lead to a longer life of the pack. (We haven’t tested the Alpha SL long enough to have an opinion—but ours is holding up nicely.)

Any keen observer will quickly note that there is, in fact, stitching on the Alpha SL. What gives? “There is a mix of constructions on the pack,” explains Ryan Hetzel, a backpack designer at Arc’teryx. “We did ‘no-sew’ where no shaping was needed, so you’ll see lamination on the upper ice-axe attachments, the ice-pick pocket, top flap, and front pocket.” On sections where curvature was required, like where the back panel connects with the sides, the pack is sewn. Graflyte—and the rest of Aluula’s line up—is still a relatively new, proprietary material, and as designers learn how to better work with it they hope to gradually reduce the overall stitch-count of a pack.

How the pack carries

Before you can climb, you have to approach, so let’s talk about how the Alpha SL carries. Its unpadded, 4mm-wide hip belt isn’t winning a comfort award anytime soon, but it was wide enough to disperse a load evenly while hiking for several hours into Howser Spires last weekend. A thin but mercifully stiff back panel dampens the feeling of an errant cam lobe or ice screw digging into your back, while the shoulder straps strike a nice balance between padded and thin enough to not restrict overhead movement. Given its small volume, we didn’t think the pack needed anymore padding to carry 30 liters worth of gear. But there were a few times—for instance while carrying a full 30-liters plus crampons, rope, and ice axes on the outside of the pack—we’d have appreciated a pair of load lifter straps to remove some of the weight pressing into our shoulders. We also liked the easily removable compression straps that allow you to attach extra gear to the sides of the pack—and even add a hip belt—on gear intensive missions, but which could be removed for superlight days. By removing all of these accessories, this pack barely tips the scales at 316 grams (11.5oz).

What’s the difference between the new Alpha SL and the Alpha FL?

The Alpha SL and the cult-classic FL share a general body shape but have a few key differences. The SL is less than half the weight of the FL—even with the four compression straps that come included. While climbing Life On Earth (5.10c; 230m) on Mt. Habrich, we also found the SL to climb more comfortably than the FL: it sits high on the hips and has a tapered bottom, two factors which facilitate hip mobility (alpine knee!) and keeps the space around your harness clutter-free. The SL also has a different ice-axe-handle lash point: a single-purpose elastic cord fixed with a plastic hook rather than the FL’s integration with an external crampon carrier. This update, while lighter, makes it harder to attach an ice axe to the pack when wearing mitts—as we learned while packing up in a 5°F snowstorm—but not by an enormous amount. (And you can always add a short loop of cord to the elastic to make it easier to grab with numb digits.)

But significant weight savings can affect a pack’s functionality: the major difference between the FL and new SL is the closure systems and how each impacts their perceived volume. The Alpha FL is a classic roll top with a 12-inch collar. The Alpha SL is also lidless, but has a triangular flap that covers the top opening of the pack as you cinch the collar tight. As a result, the SL isn’t as weather proof as its predecessor if it’s jammed to the rim with equipment. The pack’s opening will be exposed to the elements (rain, spindrift) unless it’s operating just under max capacity. The FL’s roll top, on the other hand, does an excellent job of keeping out detritus—and the generously sized roll top makes the pack feel significantly larger than the SL. Anecdotally, with both “30-liter” packs side-by-side, we were able to pack about 10 extra liters of gear into the FL’s 12-inch collar while still being able to roll it tight.

When is the Alpha SL available?

The Alpha SL will be available in a 30-liter volume in spring 2025, after which (we hope) Arc’teryx will begin releasing larger volumes. We think a slightly larger model will be much better suited for overnight missions in the alpine. We are also going to continue hammering away on this 30-liter Alpha SL in Patagonia, the Canadian Rockies, and Rocky Mountain National Park this winter, and we’ll have an updated review about its long-term performance ready for when you’re considering dropping down some cash.

Pros

• Absurdly light
• Durable
• Pack body is waterproof
• Plenty of straps that are easily stripped
• Internal floating pocket gives easy access to belay snacks
• Comfortable carry given its weight
• Rope-strap buckle is secure and easy to use with gloves
• Easy to locate gear inside thanks to white fabric

Cons

• Expensive
• Ice-axe-handle attachments could be more user-friendly
• External front pocket is too thin to use when the pack is full
• Feels small for 30 liters
• Top closure is not weather-proof

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