I often find myself in need of a framed backpack. While I love my frameless bags, most of the thru-hikes I pursue involve at least a few long water carries, heavy snow gear, or six-day food hauls. Keeping my pack weight in the magic sub-20-pound range necessitated by frameless designs isn’t always feasible. Still, I don’t love adding an extra pound of frame to my base weight.
Enter the Superior Wilderness Designs SL40: a framed, ultralight pack that can carry heavy loads without blowing up your base weight. 5083 Sheet
MSRP: $349 (some options add cost) Typical weight: 19.9 oz (pack + frame with no Y strap, back pad, or bungees*)
*Maxing out these optional add-ons would increase pack weight by 3.15 oz
**SWD delivers packs with extremely long webbing throughout for maximum body compatibility. I trimmed them to fit my needs, removing 0.25 oz from the hip belt and 0.2 oz from the load lifters and sternum strap. I did not trim the Y strap, but this is possible as well. Your mileage may vary depending on your own body and needs.
Cruising the Haute Route Pyrenees, in ultralight style
*The entire pack can be made of black Ultra 200X for a modest weight penalty. Other colors of ultragrid are available for the bottle pockets, and the outside pocket can be optioned with ultragrid instead of stretch mesh as well.
The SL40 is an ideal pack for long-distance hikers with low-volume kits but who occasionally need the extra support of a robust frame. Long food carries, winter gear, and bear cans will easily be accommodated, despite the lightweight design.
This pack saw over 800 miles of action prior to review, including the Haute Route Pyrenees (HRP), Tour Du Mont Blanc (TMB), and Walker’s Haute Route (WHR). It also saw some hard miles in America’s deserts and snowy early-season backpacking in the Colorado Rockies.
The SL40 is a framed backpack with dual 7075 aluminum tubular stays. These beefy frame pieces are exceptionally strong and stiff for their weight and will haul about anything you can fit into the pack. A pair of tubular stays weighs just two ounces, compared to the 4+ ounces of a comparable bar stock frame.
Load lifters are a piece of webbing and an adjustable ladder lock that connect the top of a pack’s frame to the shoulder straps. When the frame extends up to or above your shoulder height (as is the case with the SL40) adjusting the load lifters will shift the weight of the pack, as well as help reduce the amount of weight transferred to your shoulders.
Enjoying the view in the Pyrenees mountains. You can see the load lifters angled up from the shoulder strap, connecting to the frame. The frame extends about 5″ past where the shoulder strap is stitched.
At first glance, the SL40 may appear like a pretty basic pack. There are no hipbelt or shoulder strap pockets, no zippered compartments, and no roll-top compression straps out of the box. The core ultralight design philosophy is more about the simplicity and absence of gear, rather than getting lighter versions of complicated products. All these features add weight, and leaving them behind creates an incredible sub 20oz (1.25 lbs) framed pack that can haul just about anything.
Despite the lack of convenience features out of the box, SWD does leave a series of webbing and cord tabs around the pack to support their large ecosystem of modular accessories.
The top of the pack features three pairs of webbing loops intended for use with a top strap or Y strap. This is an important feature for transporting bear cans, pack rafts, or other bulky gear externally.
The shoulder straps have the standard daisy chain of webbing for adding on pockets, phone holders, or water bottle sleeves.
The hipbelt webbing is more minimal, sized perfectly for SWD’s hip belt pockets but not much else.
There’s one last secret webbing loop, inside the water bottle pockets. This tab is for the removable roll-top vertical compression (RTVC) straps. By default, the roll top of the pack clips to itself in a donut, rather than stretching down. If this doesn’t suit your style, they provide this easy option to revert back to a more familiar closure system.
New in their ecosystem with the SL40 is a series of cord and bungee-based accessories. Down the sides of the pack and across the bottom are a series of short cord loops. In many ways, they function similar to regular webbing loops for compression straps or holstering gear to the outside (such as foam sleeping pads or skis). The pack ships with one pair of compression bungees, but you can easily make your own lashing with shock cord or static paracord.
This pack uses a tubular (hollow circle) aluminum frame, as opposed to the bar (rectangular) frame that most packs in the sub-two-pound category have. Users of many traditional packs from brands like Osprey and Gregory will be used to seeing tubular aluminum, but it is surprisingly absent from the cottage and ultralight pack industry.
Why has SWD made the leap to a tube frame? Deep, hollow cross-section shapes are more structurally efficient than the thin and flat bars often used in packs. This means a stiffer, lighter frame that will more effectively transfer weight to the hipbelt.
At the same time, the hollow shape does introduce a potential new failure mode: local deformation, aka “denting.” Imagine what happens when you whack that cardboard tube a little too hard against your sibling or a countertop. The leading edge folds over into the hollow area and stays that way.
Theoretically, a tubular aluminum frame could experience this if it was hit or dropped too aggressively. In reality, this almost never happens. I felt the frame has a sufficiently thick sidewall to prevent this under any normal or peripheral use case. Dan Durston has also said this failure mode has never been reported in his Kakwa packs, backing up that this is an unlikely event.
The pack body with one compression bungee. In the middle is the black, tubular 7075 aluminum stay for the SL40. On bottom is a silver 7075 Bar stock frame for a SWD Long Haul 50. Despite the tubular frame weighing half as much as the bar frame, I can barely flex the tubular while the bar moves with ease.
The frame stays on the SL40 use a premium 7075 aluminum blend, produced by Easton. You might be familiar with Easton as the maker of a wide variety of aluminum products, including tent poles for many major brands and my favorite stake, the Easton Nano.
While the average backpacker may not be familiar with aluminum chemistries, this is a meaningful upgrade. The standard 6061 aluminum used in many bar frames (such as the HMG Southwest and Windrider series) is less stiff, heavier, and often deforms under heavy loads. This often means these packs get less comfortable and carry differently as they are loaded up, leading to back pain and rubbing.
Using a premium 7075 frame means consistent, high-level performance.
On a framed pack, there is a huge rift between packs that end at the shoulder strap and those that rise above by a few inches. An extended frame allows the pack to effectively use load lifters for a better, more adjustable fit and less strain on the shoulders. Ending at the shoulders makes the frame less effective, and makes load lifters ineffective. The taller the frame extends up, the more weight it can shift off your shoulders. If you are between sizes, I would recommend going for the taller size.
The weight of this pack is its show-stopping feature at just 19.9 oz (1.25 pounds) for the main body and frame. Getting a two-piece frame pack under 28 oz is hard enough on its own, and to do it with comfortable straps and a stretchy pocket is almost unparalleled.
Most hikers are going to want to add a few more convenience and comfort features, such as a top strap and some compression bungees for stashing poles. Even so, an average configuration of 22 to 24 oz beats the competition by a fair margin. I loved having the extra load-carrying capacity of the frame without having to compromise on my pack weight. It came in handy many times on unexpectedly long water and food carries.
The side bottle pocket is often a love-hate relationship on packs. When the top edge is high and cut straight across, they stay in place well but become hard to get in and out of without taking off a shoulder strap. When they are cut low and angled down towards the front, they can be accessed with ease but also tend to eject themselves when bending over.
On the SL40, I finally have bottle pockets that I can easily use, without the accidental drops. Over 800+ miles of use, I only once dropped a bottle out of the bag. In this case, it was while bending over and only having a single bottle on a side.
I think the cut height and angle is the perfect in-between, provided you use their preferred bottle configuration of two 1L sSmartwater or Lifewater bottles on each side. More on the drawback here below.
The Superior Wilderness Designs SL40 Ultra hipbelt (above) vs the SWD Long Haul 50 Hipbelt (below). The SL40 is more tapered and is sewn directly to the pack body, while the Long Haul 50 stays wide until the end, and features a “floating” design.
Despite the low overall pack weight, there is no compromise in the cushioning on the shoulder and hip belts. In fact, while most companies are using 0.375 inches of foam, SWD is using a full 0.5 inches of premium Evazote foam. Evazote is considered the best-in-class performer for lightweight padding because it rebounds better and longer from compression.
Something about the spacing, padding, and shape of the shoulder straps also makes the sternum strap unnecessary for me. This obviously won’t work out for everyone, but to me it indicates a high level of refinement missing in many packs.
Another small detail is that SWD uses the finishing ⅛-inch layer of spacer mesh “wrong side out,” meaning that the part you touch and feel is a smooth black fabric instead of a series of pea-sized holes that easily snag pine needles and dirt. I prefer this layering over the alternative “right side out” that usually collects little rocks and needles over the course of a trip.
The SL40 has an option for an Ultragrid or Venom Mesh outside/back pocket. I decided to use Venom Mesh hoping its stretch would help keep things in place, whether it is filled up or hardly used.
I was a little concerned when unboxing that the mesh was too tight, with no pleats at the bottom and only a little spare fabric at the top. My concerns quickly faded as I started to load it up with all my “outside” gear. I was typically able to fit a water filter, 2L empty bladder, rain jacket/pants/gloves, sunscreen, spare snacks, and even occasionally an Alpha Direct fleece before I felt it was truly maxed out.
The Venom Mesh pocket punching above its weight class. Yes, that is a bag of chips sticking out of the top.
As mentioned above, this pack is slimmed down to only the essentials. Convenience features, such as hip belt pockets and complicated compression systems, are left out in favor of simplicity and lightness.
While their ecosystem of removable accessories can make up most of the difference, having them completely removable means there is extra overhead in materials and hardware. If there is a feature you always use and can’t live without, such as shoulder strap bottle sleeves, they are going to weigh more and function just a bit worse than having them built in from the start.
Some options can be built in via an a la carte “custom” order page or negotiated by email, but these will make the pack un-returnable in case of mis-sizing or other issues.
The current iteration of the SWD Y-strap is a bit better than the last, with the pack attachment points using a captive clip for the ladder locks rather than a large “G-hook.” Even still, having all three pack attachment points and one of the side-release buckle pieces adjustable makes it a bit annoying to manage and leaves lots of loose ends that can flap in the wind. I would personally prefer they take this down to just two (one for the V part of the strap, one for the straight part) and leave the rest as low profile, fixed bartacks.
Similarly, the side compression shock cords are easy enough to operate, but moving them requires a bit more work and a knot (girth hitch) to attach to the cord loops. I actually prefer this system, but moving them to different positions after cinching was a bit of a pain.
The sewn-in hipbelt on this pack is fairly comfortable but is not quite as good at transferring heavy loads as the larger, “full wrap” hipbelt found on SWD’s other framed pack. The “Wing” design used here is likely to perform worse for people with large waists as well, since the padded section will not wrap very far towards the front.
On a late-season desert trip, I ended up carrying 14L of water into a canyon to set up a basecamp. The pack held up to my 38-pound total pack weight fine, but I just couldn’t quite get comfortable with the hipbelt after the first few miles. This eased off significantly once the total weight was more in the low 30s, and after a few more weeks of hiking where my body was better adjusted to wearing a pack all day.
Those consistently carrying mid-30s loads may want to look to packs with a more complete hipbelt design.
Currently, the SL design is only available in a 40L internal volume design. This is manageable for most ultralight backpackers, but in practice I found it a bit tight for long food carries. With a bulky two-person DCF tent hogging my internal volume, I often had to strap my food bag to the top using the Y strap when carrying more than four days. Perhaps if I used a more compact silpoly tent or didn’t love potato chips so much, I could get to five days internally.
The scuttlebutt online is that an SL50 (50-liter internal volume) will be released eventually, but I haven’t seen any commitment to that on their website so far.
A 4++ day food bag strapped to the top since it didn’t fit inside my bag.
I ended up really liking the bottle pockets on this pack but realized quickly they were optimized only for Smartwater bottles. I find Smartwater bottles comically tall and often opt for Essentia’s similar, but shorter and fatter, one-liter bottles instead. The slight difference between the two shapes was enough that fitting two Essentias on each side was a tight squeeze. I couldn’t access them while walking, while Smartwater-shaped bottles were a breeze.
Similarly, 1.5L Essentia bottles could work by themselves but were awkwardly tight in one direction while wobbling a bit in the other. I ended up just having to commit to the tallest, skinniest 1L bottles I could find to make it work with ease.
Challenge Outdoors, the manufacturer of the Ultra fabrics used on this pack, recommends taping seams for stability and strength. This has the added benefit of making the pack highly waterproof since the fabric itself is waterproof as well. Missing this part of the construction isn’t the end of the world, but it does mean you’re missing out on a nice layer of extra protection and stability.
If you want your pack taped, it’s a hefty $75 custom charge from SWD and will add about two ounces to the total weight. You can also buy a full roll of tape from Ripstop by the Roll for about $40 and do it yourself, with the added benefit of keeping the leftover yardage for repairs of all your laminate products (such as EPLX and DCF). Note that if you tape yourself, you will need to let the tape’s glue cure for about 24 hours before use for full adhesion and strength.
The Superior Wilderness Designs SL40 Ultra is an incredibly light pack that can also haul heavy loads when called to duty. In many ways, it makes a perfect bag for mountain west thru-hiking (such as the PCT or CDT), where generally conditions make a low base weight easy to achieve, but you might need to pack on the weight for those few long water carries, six-day resupplies, or stints of snow hiking with an ice axe and bear can.
At $350, this pack falls in line with industry pricing on framed ultralight bags. I think it is an great value for a unique product, and I trust it to last many more miles of long-distance hiking. Given the high standard these packs are made to and their small-shop domestic production, the price is more than reasonable.
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The Superior Wilderness Designs SL40 Ultra was donated for purpose of review
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I've hiked thousands of miles across the deserts and mountains of the world. I like to push my limits, whether its big miles on trails or difficult terrain off trail. When I'm not in the wilds, I love to geek out on maps, gear, and hiking skills. My major trail adventures include: Long Trail (LT) 2018 ||| Continental Divide Trail (CDT) 2021 ||| Nolan's 14 2021 ||| Pfiffner Traverse 2022 ||| Skurka's Wind River High Route (WRHR) 2023 ||| Haute Route Pyrenees (HRP) 2024 ||| Tour du Mont Blanc (TMB) 2024 ||| Walker's Haute Route (WHR) 2024 ||| Uinta Highline Trail (UHT) 2024 ||| and a few thousand miles of unnamed routes and adventures in between.
Great review Alex. The pack seems very well made, but definitely has some limitations. Could you explain why one would choose a floating hip belt over a fixed/sewn in belt? I’m guessing a floating belt is more flexible. But is it necessarily needed? What are your thoughts?
6061 Bar Notify me via e-mail if anyone answers my comment.