Hyperlite Mountain Gear Unbound 40 Ultralight Backpack Review

Even if you haven’t noticed, you’ve probably seen more than a few backpacks from Hyperlite Mountain Gear around. Their simple design and subdued black and white color scheme are instantly recognizable, as are the grody thru-hikers attached to them. Once a rare and highly coveted item reserved for only the most hopelessly afflicted ultralight backpacker, HMG packs have built a solid reputation for being durable, lightweight, and dependable over the long haul. Now they’re pretty much everywhere.

While they’ve been a hot item on the long trails of the world for the better part of a decade, HMG’s newest backpack is more enticing than ever. Designed specifically for thru-hiking, the Unbound refines many of the features that have made previous packs a smashing success. But how much could HMG really improve on something that was already so simple? That’s what I aimed to find out after getting my hands on the Unbound 40. Is it really the best HMG backpack for the AT, PCT, or CDT?

Hyperlite Mountain Gear Unbound 40 At-a-Glance

I spy with my little eye, some features that are different from other HMG backpacks.

MSRP: $369+
Weight: 30.1 ounces (size M)
Available sizes: S, M, L, T (torso sizes: 15”-21+”)
Volume: 40 liters internal, 9 liters external (55L version available)
Max. recommended load: 40 pounds
Pockets: 1 main compartment, 1+ front mesh, 2 hip-belt pockets, 2 side pockets, 1 bottom mesh
Frame: Single, contoured aluminum stay
Material: DCH50 and DCH150 (aka DCF)

Intended Use

While HMG packs are no stranger to the longest thru-hikes, the Unbound 40 has been designed specifically with über-long backpacking trips in mind. This thing isn’t your weekend Airbnb. Nope, you’re moving in indefinitely. Sell your car, ‘cause you ain’t gonna need it where you’re going. In fact, HMG’s entire Unbound product line was created with thru-hiking in mind.

Not that you need to live in the dirt for months when carrying the Unbound 40, but this thing is supposedly ready and capable of going the distance. Relative to their other backpacks, HMG emphasized pocket accessibility, which might seem like a subtle and boring focus. However, it’s the small things that matter day after day, snack break after snack break.

Circumstances of Review

Thinking about life and Dyneema Stretch Mesh near Cottonwood Pass on Collegiate West. Photo credit: seigenbrot

After gushing about how the Unbound 40 will survive months of on-trail abuse, I’m chagrined to admit that I haven’t even come close to pushing this pack to the limit. However, based on my experience with other HMG packs, I feel qualified to comment on the long-term durability of the materials and craftsmanship. Furthermore, my week on the CDT’s Collegiate West section combined with other hikes in the Sawatch Range, provided ample opportunity for me to form a few strong opinions about the Unbound 40.

HMG Unbound 40 Features

Yo, check it out, the dual-access mesh pocket. Both openings lead to the same place.

DCH construction: This stands for Dyneema Composite Hybrid, which is pretty much the same stuff as legendary DCF. While DCF is a popular choice for ultralight shelters, it suffers from some drawbacks that make it a less-than-ideal material for backpacks. That’s where DCH comes in — it’s that same awesome DCF with an added outer layer of woven polyester. This builds on the awesome properties of DCF and boosts abrasion and puncture resistance to levels worthy of a long thru-hike.

Single frame stay: A single aluminum stay runs down the spine of the Unbound 40. Aside from the semi-rigid foam/plastic back panel, this is the only frame structure of the backpack. This is a departure from most other backpacks which typically use two stays, including most HMG packs.

Dual-access mesh pocket: HMG has tweaked the ubiquitous, large mesh pocket by adding another access point a few inches above the bottom. Don’t worry, everything is still secure, but this makes it easy to find the small things that typically disappear. I can guarantee that I didn’t describe this well, so I’m hoping the pictures will bail me out.

Bottom pocket: On the very bottom of the pack, there’s another stretchy mesh pocket that can hold just about anything — snacks, rain gear, maps, you name it. One side is completely open for rummaging, and there’s a tiny access port on the opposite corner for stuffing in your snack wrappers.

Y top strap: Nothing special here, but you gotta have it. An adjustable Y-strap clips across the top of the roll-top closure and has plenty of slack for securing bulky items such as a foam sleeping pad, bag of chips, or bear canister.

Roll-top closure: Dry bag style. This helps seal out the elements while also helping to keep the pack tidy as the volume fluctuates during your hike. Expand the extension collar for those big food hauls, or roll it way down when you’re running on empty. You’re looking good either way.

The top strap keeps snack break essentials handy. My sit pad and chips are just one clip away.

Completely seam taped: DCH is 100% waterproof when new, but the sewing process compromises this by poking tons of holes everywhere. To regain weather resistance, HMG seam tapes all sewn points. It’s dangerous to consider any backpack fully waterproof, but the Unbound comes close.

Dyneema Stretch Mesh: A first on HMG packs, the Unbound uses a new wonder-mesh, which combines the durability of Dyneema with the stretchiness of stretchy mesh. At least in my limited experience, this stuff is awesome. Extension is great, so the large mesh pockets can hold a ton of stuff. And HMG must be confident in its durability to use it for the bottom pocket, the most abused area of a backpack.

Already familiar with HMG backpacks? Here’s what’s new with the Unbound 40

The Unbound, aside from having its own bumper sticker, is different from the classic HMG packs. Oooh, ahhhh, Dyneema stretch mesh.

HMG has been making awesome lightweight backpacks for many years now. In fact, their success and popularity have garnered so much attention that their Southwest packs are available at mega-retailer, REI. While the design has been tweaked over the years, HMG’s three most popular packs for thru-hiking (Junction, Southwest, and Windrider) are essentially the same. The outer pocket material is the only difference.

So while the Unbound actually looks different from these three common thru-hiking characters, what has actually changed? Is it a completely new pack, or yet another reimagining of the same old, albeit excellent, thing?

To dream up the Unbound, HMG claims to have looked hard at the essential needs of thru-hikers. The result? A new emphasis on accessibility — keeping the essentials on hand while keeping the pack on the shoulders. Sure, previous HMG packs were good for thru-hiking, but the Unbound is designed specifically to keep hikers hiking longer. Here are the major differences:

Side pockets: The water bottle pockets are larger to accommodate water bottles, a cook set, tent poles, etc. better. In my opinion, the side pockets were one of the weakest parts of the classic HMG packs (they squeezed out empty bottles), so I’m thrilled to see this upgrade. These pockets are huge and easy to access. Grabbing and replacing a water bottle is as easy as ever for those with reasonable shoulder mobility. An adjustable drawstring also helps secure items that would otherwise float loosely.

This isn’t a revolutionary design (they’re almost identical to my favorite side pockets ever on the Granite Gear Crown2 60), but it’s awesome to see them finally incorporated by HMG. This is the most significant upgrade, and it’s a big one, even if it seems boring.

Removable hip belt: Considering that a hiker’s weight can fluctuate significantly over the course of a thru-hike, or just life, having the option to change the hip belt size can keep the Unbound in use through these changes. Other HMG packs have sewn-in hip belts, which means that your torso size determines your belt circumference regardless of your personal measurements.

And if you don’t like hip belts at all or for a specific trip, then you can remove yours without taking scissors to an expensive pack. Replacement hip belts are available through HMG’s website.

Dyneema Stretch Mesh: This is the first time HMG has used a stretchy material for the large external stuff pocket. Functionally, this doesn’t change the utility, but it does result in a more secure fit and streamlined appearance.

The bottom pocket is made from Dyneema mesh and is a good place to keep snacks. Also, notice the orange daisy chains and massive side pockets.

Bottom pocket: This is yet another pocket that keeps stuff within easy reach while wearing the pack, and is unique to the Unbound among HMG packs. Honestly, I couldn’t figure out how to use it effectively, but had some success storing snacks. I think it would be a good home for gloves and a beanie too, but not other clothing items that require removing the pack to put on. For these you need to take off the pack anyway, so why store them in a vulnerable position on the bottom of your pack? Anyway, a cool pocket if you figure out what to keep in it.

And for what it’s worth, I sucked at stuffing snack wrappers in the small corner port. My fingers ain’t big, but they felt too large to pull off this fiddly maneuver.

Single frame stay: The Unbound has a single aluminum frame stay, which is half the number used in HMG’s other packs. Removing a rod of metal is obviously good for cutting weight, but doing so must reduce the weight capacity versus other models, right? Not according to HMG. The Unbound is still rated to 40 pounds. Suspicious? Me too, but no complaints so far.

Externally bound seams: The Unbound seam structure is different and better. Not only are the seams bound (read: strong), but they are also on the outside of the pack, which makes internal seam taping easier and more effective at keeping moisture out. Practically, the external seams are also combined with daisy chains to provide beaucoup attachment points.

Side compression: Gone are the no-stretch webbing compression straps of other HMG packs. The Unbound utilizes adjustable shock cord to secure large items and keep the main pack body tight. Move this up and down the daisy chains as needed or remove it altogether.

Smaller hardware: Webbing and buckle size have been reduced on the pack body for the minor weight savings. It all works the same, but is lighter duty.

Weight: Even with all these changes, the Unbound pretty much weighs the same as the other popular HMG thru-hiking packs. This is impressive given that there are real improvements, but nothing is free. The single frame stay and smaller buckles certainly diminish performance/durability. Hopefully, not a noticeable amount.

How’d it do?

The HMG Unbound has been easy to use comfortably no matter the conditions. Photo credit: SpiceRack

The HMG Unbound 40 is a great backpack. I literally have no real-world complaints, and if I could figure out a solid use for the bottom pocket then I would like it even more. However, I must add that backpacks are highly personal. I love the simplicity of the Unbound and similar packs, but if you want more than the most basic features, then you might want to keep looking. That said, the HMG designed the Unbound for a specific purpose, and in that it excels.


The side pockets are awesome. I love how much they hold and how easy they are to use while remaining secure. The adjustable drawcord keeps things from squirting out or flopping around, no matter how much stuff is in them. Yep, these pockets are a major improvement over those on other HMG packs.


Although I never loaded my Unbound to the 40-pound limit, I also never had reason to complain about the comfort. At first look, I was worried that I’d feel the single aluminum stay on my spine, but I never noticed it. The foam back panel did a good job of padding that spot and keeping a nice flat interface for my back even when the pack was stuffed full. No barrelling, at least in my experience.

I’ve used cushier hip belts and shoulder straps before, but those on the Unbound are plenty wide and supportive. They are perfectly unremarkable, neither good nor bad, not better or worse.

Despite finding that the Unbound fit me well, this won’t be true for everyone. If you can, try before you buy. While the Unbound is hard/impossible to find in stores, their Southwest is available at REI and is a great place to start.


Without 2,000+ miles with my Unbound, I can only speculate about how well it will hold up over the course of a thru-hike or two. With this in mind, I don’t think that there is anything to worry about. The base HMG DCH construction is a proven quantity, known to last for multiple thru-hikes.

The new Dyneema Stretch Mesh is the biggest question mark, but it feels far more durable than the stretchy stuff used by other brands such as Gossamer Gear, REI, Osprey, and Granite Gear, which have gone the distance before. If anything does wear out, it will be that confounding bottom pocket. However, if the Dyneema mesh is everything it’s cracked up to be, then that will take a while.


You already know that I love the side pockets and am confused by the bottom pocket. Other than those, the hip belt pockets are cavernous and easy to use, and webbing on the shoulder straps can accommodate aftermarket shoulder pockets if that’s your jam.

Finally, the large, stretchy front pocket is as good as they come. That fancy Dyneema mesh really does stretch a lot so I was able to keep all of my usual things in there with room to spare. Regarding the dual-entry feature, I think that it’s a smart tactic for improving accessibility with zero sacrifice. I did find it handy for grabbing my poop kit nice and quick when the urge called, and I anticipate being surprised by its usefulness for many miles to come.

Bear Canister

The Unbound 40 can handle your standard ~11-liter bear canister like most other backpacks in this category. Pack it inside vertically, or use the long Y-strap to secure it outside, on top.

HMG Unbound 40 Pros

A lot of features on display here. Look how much stuff is in that side pocket!

Pockets: HMG nailed the pockets when they designed the Unbound. If there was ever a weakness with the other HMG backpacks, then it was the side pockets. Bigger, more secure, and easier to access, they are better on the Unbound in every way. Additionally, I truly believe that the Dyneema stretch mesh is darn near an ideal material for the large stuff pockets.

Lightweight: There are lighter packs out there, but the Unbound can do a lot for one that weighs less than two pounds. The load capacity and durability in particular set it apart versus most other backpacks this lightweight.

Durability: DCH is a proven material. It survives long trips in rugged terrain despite its low weight. The Unbound joins a time-tested line of HMG backpacks that are known to survive the longest trails without issue. The only question mark is the Dyneema mesh, but I’m confident that time will prove this to be one of the most durable stretchy fabrics available.

Simplicity: With just one main compartment and a few outer pockets, the Unbound is your classic UL design. While some folks might like a few more bells and whistles, the simplicity keeps organization easy and focused. Plus, there’s still a whistle on the sternum strap and you can add a bell.

Removable hip belt: All bodies are different, and a replaceable hip belt will help the Unbound fit more of these bodies comfortably. This is a refreshing and long-awaited addition from HMG. It is unclear whether or not it is possible to save $50 by swapping hip belt sizes when you originally order.

HMG Unbound 40 Cons

No hydration port, or hydration sleeve, in sight. Check out that single frame stay too.

No load lifters: These useful straps are rare on ultralight backpacks, but that doesn’t mean they aren’t worth their weight. Running from the top of the shoulder straps to the top of the back panel, they can lift some of the load off the shoulders and also adjust how close the pack conforms to the back. I missed these on the Unbound. But I get it. With a single frame stay, there’s not enough structure for load lifters to make sense. 

No hydration port: I could not locate a hydration port if there is one. The side pockets are capable of keeping plenty of water within reach, but if you like drinking from your dangly straw, then you’re out of luck.

Final Thoughts

For thru-hiking or peak-bagging, the Unbound 40 is a keeper. Photo credit: SpiceRack

HMG did a great job with the Unbound 40. It is easily my favorite of their backpack offerings, mostly because of the improved side pockets. However, almost all the other differences between this pack and their others (Junction, Southwest, and Windrider) are improvements in my book as well. While all the tweaks are relatively minor, they make a noticeable difference every day when in the backcountry. HMG sought to build a pack for thru-hikers, and they succeeded.

If I have any reservations at all, they relate to the frame. It’s hard for me to imagine that the single aluminum stay functions as robustly as the double stay system used in most other similar packs (including others from HMG), yet the load rating is still a substantial 40 pounds. With neither the desire nor fortitude to truly put this number to the test, I’ll need to take them at their word. And I’m cool with that. If I plan to carry a load that large for any amount of time, then I’ll probably consider a different backpack anyway. The Unbound is ultralight, so it’s advisable to keep max loads as close to 30 pounds as possible.

All things considered, the Unbound is a top option for folks in need of a new backpack. It takes the legendary awesomeness of HMG’s time-tested DCH design and makes very real improvements. I won’t be surprised at all to see this overtake the others as HMG’s most popular pack on the long trails of the world.

Shop the HMG Unbound 40

Similar Lightweight Backpacks

Hyperlite Mountain Gear Southwest 40
MSRP: $349
Weight: 30.8 ounces
Capacity: 40 liters
Max. Load: 40 pounds
Material: Dyneema Composite Hybrid

Durston Kakwa 40
MSRP: $250
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Max. Load: 45 pounds
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Read our review of the Durston Kakwa 40 here.

Zpacks Arc Haul Ultra 50L
MSRP: $399
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Max. Load: 40 pounds
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ULA-Equipment Ultra Circuit
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Six Moon Designs Swift X
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Disclaimer: The Hyperlite Mountain Gear Unbound 40 was donated for the purpose of review.

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Comments 3

  • thetentman : Oct 12th

    Thank you for a very thorough review. If my Dana Designs packs ever wear out I will consider this pack.

  • Miki : Nov 9th

    After reading your Switchback-Zlite sol review, why is there the Thermarest zlite sol, not Switchback on your backpack photos? 🙂

    • Owen Eigenbrot : Nov 9th

      Hahaha, I’ve been WAITING for someone to call me out on that! That’s the same Z Lite that I used for the comparison article, and I’ve just been trying to wear it out before replacing it with a Switchback. I couldn’t, in good conscience, give the inferior pad away or toss it in the trash, so I’m the lucky guy who gets to use it for years. And now that it has so much sentimental value, it’s going to be hard to give up. Darn.


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