Hyperlite Mountain Gear Unbound 40L Backpack Review

Hyperlite Mountain Gear Unbound 40L

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This is an in-depth review of the Hyperlite Mountain Gear Unbound 40L Backpack in 2024. This is the latest ultralight backpack from Hyperlite Mountain Gear and possibly the best to date.

If you’re tired of carrying a heavy backpack loaded full of too much gear and want to lighten your load, then a lightweight backpack will be something you will need. And the New HMG Unbound 40L Backpack is their best effort yet. This 40-liter pack is not only ultralight but waterproof and has some handy features that most other packs do not have.

I’ve hiked almost 10000 miles / 16000 km in the last few years on many of the best thru-hiking trails in the world. I’ve used and tested most of the best backpacks that you can buy. As a result, I know what separates a good backpack from an average one.

So, I going to take a look at the Hyperlite Mountain Gear Unbound 40L Backpack and see if they deliver one of the best ultralight backpacks on the market in 2024.

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How We Tested

The Hyperlite Mountain Gear Unbound 40L Backpack in this review has been extensively evaluated and researched by the expert author who has more than 30 years of experience in Thru-Hiking, Backpacking, and Hiking. He also spent several years managing a hiking retail store and is regarded as an expert in this field. The backpack was supplied by the manufacturer. It has been rigorously tested by the author in all kinds of weather on several backpacking trips. The research, testing, and experience of the author have combined to produce this honest review. Read the Review Policy for further details.

In-Depth Review: Hyperlite Mountain Gear Unbound 40L 2024

Hyperlite Mountain Gear Unbound 40L Review

Hyperlite Mountain Gear Unbound 40L Review

Weight: 30.1 oz / 853.3 grams

> Lightweight
> Waterproof
> Good access to side pockets
> Multiple external storage options
> Comfortable even with a bit of weight in the pack
> Very Durable
> Not good for anyone who wants to carry a lot of gear
> Only come in 40L Capacity

The Hyperlite Mountain Gear Unbound 40L is an ultralight backpack targeted at anyone wanting to lighten their load on their next overnight backpacking trip or multi-month thru-hike.

Although it is called the Unbound 40L, it has a total of 49-liter capacity. With a 40L capacity in the main bag and 9L of storage in the side and rear pockets.

This smaller-sized pack will not be for everyone. But once you have a light and compact sleep system, have removed all your unneeded luxury items, and want to set off with minimal stress on your body then this is for you.

With multiple external storage locations, it is perfect for finding a place for your wet rain jacket after that short rain shower. Speaking of rain, rest assured that your gear will stay dry in this waterproof backpack that even has seam sealing to ensure your gear stays dry.

The side pockets are the perfect place for carrying several liters of water during that desert section of the trail. Hyperlite Mountain Gear put some thought and effort into the external storage areas on this pack.

Overall, this is the perfect backpack for thru-hiking or those shorter multiday backpacking trips where you don’t have too much stuff. A real favorite for minimalists.

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Frame, Harness, and Hipbelt

The backpack is held in shape by a verticle aluminum stay that is surrounded by 1/4 inch foam and then covered with the Dyneema Material. This combination does a good job to keep the pack in its original shape.

The Shoulder Harness is comfortable and has the option of adding some extras to allow you to customize your pack harness. Items such as a camera pod, shoulder strap bag, or a small fanny bag such as the vice versa that can strap across the sternum strap give added gear carrying flexibility.

It is refreshing that the hip belt comes with waterproof side pockets. I love these. Perfect for money, keys, lip balm, sunscreen, snacks, phones, headphones and so much more. It is even big enough to fit most ultracompact Hiking Cameras. They come complete with a waterproof zip and are big enough to keep most people happy. And if you want to be ultralight, you can remove it, or replace it which is a good option if you gain or lose weight. Or maybe you want to share the pack with multiple people.

Hyperlite Mountain Gear Unbound 40L hip belt pocket
Good access to very good waterproof hipbelt pockets


At 30.1 ounces or 853 grams which places this backpack at the heavier end of ultralight backpacks, but well within the lightweight backpack category. There are many other backpacks on the market that are lighter but few will be made as well as this.

Hyperlite Mountain Gear Unbound 40L Ultralight Backpack
Testing the HMG Unbound 40 backpack on a coastal trek

Load carrying base weight

Hyperlite Mountain Gear recommends that the Unbound 40L backpack has a load limit of around 40 lb / 18 kg. With a lightweight base weight of around 10 lb / 4.5 kg and under this backpack hardly feels like it is on your back. It is super comfortable and does a good job of distributing most of the load onto the hip belt.

When I tested the backpack with heavier loads I found it was able to carry the loads quite well. Like all ultralight backpacks, you must be careful when packing. You must ensure there are no sharp objects against your back. Even though there is a padded section between your gear and your back, it is only 1/4 of foam, so not good enough to stop an object like your cooking pot from poking into your back. Pack your backpack carefully.

If you are looking to buy a backpack like this, then you already have lightweight hiking gear or will be buying some soon. Just don’t have heavy gear in this pack, commit to carrying less and you will love the HMG Unbound 40L Backpack.

Hyperlite Mountain Gear Unbound 40L carrying a heavy load


The HMG Unbound 40L backpack uses a couple of different materials, namely Dyneema Composite Hybrid Material on the main body of the pack, Dyneema Stretch Mesh on the back and bottom pockets, Hardline with Dyneema on the straps, nylon daisy chain webbing and nylon elastic compression straps on the side to secure your water bottle, tent poles or trekking poles.

Dyneema Composite Hybrid Material in two different weights, namely DCH50 and DCH150. The Dyneema Composite Hybrid Material is stronger and more abrasion resistant than normal Dyneema Composite Fiber.

Normal Dyneema Composite Fiber is 100% waterproof, but the hybrid construction of the material is not 100%. For most purposes, it is so close to 100% waterproof that you should worry too much about your gear in a rain storm. Just don’t use the backpack as a floatation device on a river. Or use a dry back when canyoning or pack rafting.

During initial testing, there was no rain. So I loaded the pack with all my gear and poured water all over it. As expected everything stayed dry.

The back pockets and bottom pocket uses a relatively new product called Dyneema Stretch Mesh. I’m unable to comment on the long-term strength and durability of this product as there are not too many backpacks made with this material.

During testing, I tried to poke a hole in the material with sticks and failed. As I type up this review I decided to try and poke a hole in it with a pen. The pen was able to go partway through the material and be removed without ripping any of the material. So, all looks good for the long-term strength of the material. It is certainly better than what most other brands use at the moment. I wonder how long before Dyneema Stretch Mesh is more widely adopted by other brands.

Size and Capacity liters

The Hyperlight Mountain Gear Unbound 40L backpack comes in only one size, being 49 liters. It has a generous 40 liters of internal storage and 9 liters of external storage in the form of rear and side pockets.

The design of the pack allows the main compartment to expand quite a bit for those times you may have a big load to carry. Like the first day leaving town when thru-hiking. Thanks to the roll-top design and compression straps the pack can be closed to a smaller size when needed. I’m a fab of roll-top closures on backpacks.

The rear pockets have an unusual system of 3 pockets. There is one main pocket at the rear, another located further down on the rear, and one underneath.

The main rear stretch pocket uses Dyneema Stretch Mesh material. It is a generous size, strong, and has good stretch properties. When I tested this backpack I found this pocket to be perfect for storing rain gear, snacks, sunscreen, trash, and toilet paper.

It is also connected to a smaller outside pocket that can be used to access items at the very bottom of the main pocket. The smaller stretch pocket is not very big but could also be used to store items such as light snacks, sunscreen, or toilet paper.

There are also some handy daisy chain webbing loops on the back that could be used to attach something like a hiking permit tag, hand sanitizer, or similar. Although there are no ice axe loops I’m sure you could use the webbing to make something work. I guess the daisy chains could be used for anything your imagination decides, a small carabiner with a drinking mug, maybe.

As for the pocket underneath the pack, it is a stretch pocket that opens from one side only. I question the durability of this bottom pocket, even if it is made with Dyneema Stretch Mesh.

During the testing of this product I would throw the pack on the ground fully loaded and sit on the ground with the pack still on my back I had no issues but I’m not sure how the pack would look after a few hundred days of me doing this. Having said that, it is a good place to store something like your sleeping pad.

The HMG Unbound 40L features 2 side pockets which are a generous size and big enough for a couple of water bottles. I was able to fit a 2x 1L bottle in each pocket for a total of 4 liters of water carrying capacity. It could be stretched to carry a little more than that if you use water bladders such as the Platypus range of bladders.


The pack is made with one of the strongest and most durable versions of the Dyneema Fabric. As such this pack is more durable than some other Dyneema Backpacks on the market from other manufacturers. This added durability comes at the slight cost of weight. This pack is a little heavier than similar designs from other manufacturers. That is the trade-off when it comes to ultralight backpacking. Durability vs weight.

Overall, you should not have any issues with this pack. It is very durable. I only question the long-term durability of the Dyneema Stretch Material on the bottom side of the backpack. Time will tell on that one. Having said that, the Dyneema Stretch material is much better than almost any other mesh material that I have seen or used.

Water resistance

As mentioned in the material section of this review, the material is waterproof but not 100%. I would not use this backpack when pack rafting as an example. But I am confident that you will have no issues when using this backpack in the rain.

Of course, anything on the outside of the pack, whether in the side pockets or rear pockets will get wet.

Sizes and Fit

The HMG Unbound 40L backpack comes in 4 sizes, namely Small, Medium, Large, and Tall. I found the sizes to be exactly as stated but with enough wiggle room to allow you to fit into multiple sizes, especially if you are in-between sizes.

Check out the Sizing Guide on the HMG Unbound product page. Look for the link ‘Help Me Pick My Size‘.

Hyperlite Mountain Gear Unbound 40L Backpack size and fit

Carrying Water – pockets or water bladder pocket

The Unbound has larger side pockets than their cousins the South West and Windrider. With the larger side pockets comes a better and more secure way to carry water bottles or a water bladder. There is no ability to attached and use a hydration bladder within the backpack.

HMG Unbound 40L vs other backpacks

The HMG Unbound is up against some stiff competition in the ultralight backpack market. Some of the stiffest competition comes within their own lineup of backpacks, the HMG Southwest, HMG Junction, and HMG Windrider.

It could be said that the Unbound is a lighter and more basic version of the Junction with more external storage options and built with lightweight thru-hiking in mind. And for that function, this backpack excels.


The Hyperlite Mountain Gear Unbound 40L comes in at around $369 at the time of this review. That places it at the higher end of the price range for ultralight backpacks. There are a couple of ultralight backpacks that are more expensive but in my opinion, the quality of this top-tier backpack makes it worth the cost.

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The new Hyperlite Mountain Gear Unbound 40L Ultralight Backpack is one of the better backpacks on the market in 2024. There is very little to fault in this pack and a lot to like. For example, compared to other lightweight packs the HMG pack seems to be more durable and should last a bit longer than some other packs. But at 49 liters of total capacity, it is very much for the ultralight backpacker who has already dialed in their ultralight backpacking gear.

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Hyperlite Mountain Gear Unbound 40L Backpack Review
Testing the Unbound tent and backpack on a coastal trek
Another one of the Best Backpacking Gear Reviews from BikeHikeSafari.

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Frequently Asked Questions

Are Hyperlite Mountain Gear Backpacks any Good?

Hyperlite Mountain Gear makes some of the best lightweight and ultralight backpacks on the market. The new Hyperlite Mountain Gear Unbound 40L is a great lightweight backpack. So is the HMG SouthWest, HMG Windrider, and HMG Junction models.

Hyperlite Mountain Gear Unbound Backpack 40L Pin

BikeHikeSafari Gear Review Process

The author, Brad McCartney from BikeHikeSafari is a small independent adventurer and outdoor gear tester who owns and runs BikeHikeSafari.com.

BikeHikeSafari is not part of a large blog network and is proudly independent. All reviews on this site are independent and honest gear reviews of outdoor products by the author.

The author, Brad McCartney is a very experienced triple crown thru-hiker, adventurer, and bike tourer having spent 1000s of nights sleeping in a tent and sleeping bag (Read more). He was a manager of an outdoor retail store and is very experienced in what is important when using and testing gear for reviews like this.

BikeHikeSafari will never receive any money for reviews and they do not accept sponsored reviews on this website. All the comments about the gear reviews are from the author based on his years of experience. Hope this independent review was helpful for you.

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About the Author:
Brad is an Australian who has completed the hiking Triple Crown after he hiked the Pacific Crest Trail, Continental Divide Trail and Appalachian Trail. He has hiked on every continent (except Antarctica) and has cycled from Alaska to Ecuador. He is an expert on outdoor gear currently living in Chile.

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