Philip J. Smith's Blog: Hyperlight Mountain Gear 3400 Southwest Backpack Review

The Hyperlight Mountain Gear 3400 Southwest Pack is a rugged multi-day cuben fiber backpack.

The Hyperlight Mountain Gear 3400 (55L) Southwest Backpack is a durable cuben fiber backpack that’s good for multi-day backpacking trips in rugged terrain. The 3400 Southwest is basically the same pack as the smaller volume Hyperlight Mountain Gear 2400 (40L) Southwest Backpack (SectionHiker Gear of the Year in 2015) but with a longer extension collar, so you can stuff more gear inside. This is handy if you need to carry a few more days of food, extra clothing, or more sleep insulation on longer trips or in colder weather.

Internal Storage and Organization

The Hyperlight Mountain Gear 3400 Southwest Backpack is laid out in a traditional ultralight style with a large main compartment, side water bottle pockets, and a large rear pocket.

The HMG 3400 Southwest has a dry bag style roll top and solid external pockets

The main compartment has a dry bag style closure system which provides excellent top compression for stabilizing your load. The fabric of the cuben fiber pack body is also waterproof and the interior seams of the pack are seam taped, making the pack highly resistant to rain.

The main compartment has a mesh hydration pocket and hydration loop if you want to carry a water reservoir/hose inside the main compartment. Since I prefer using water bottles, I use this pocket, which lies in between the two frame stays, to store maps instead.

Interior of main compartment showing mesh hydration pocket and taped seams

Interior of main compartment showing mesh hydration pocket, hang loop, and taped seams.

There are five external pockets on the 3400 Southwest Pack, two side water bottle pockets, a larger rear pocket, and two hip belt pockets. All of the pockets are made of solid 210 denier Dyneema reinforced nylon (Dyneema Hardline), enabling the pack to be used roughly or in off-trail conditions that would quickly shred mesh pockets.

The side water bottle pockets are large enough to comfortably fit 1 liter water bottles together in addition to tall skinny items like trekking or tent poles, and have drain holes at their base. The bottoms of the pockets are reinforced at the base with a 150 denier cuben fiber/polyester to prevent punctures or tearing – an important durability feature. Water bottles stored in the side pockets are also reachable and replaceable while wearing the pack, a must-have.

The rear pocket is large enough to store my hammock tarp, cook pot, wood stove, stake bag, hydration reservoir and sawyer filer, as well as extra rain layers - basically the stuff I don't want in the main compartment because it's wet or smelly.

The rear pocket is large enough to store my hammock tarp w/snakeskins, cook pot, wood stove, stake bag, hydration reservoir and sawyer filter, as well as extra rain layers – basically the stuff I don’t want in the main compartment because it’s wet or smelly.

The rear pocket is large enough for me to store all of my wet gear, such as a tarp, tent fly, or wet rain gear, my water filter, and smelly items like a wood stove that I don’t want inside the main compartment. I also use this pocket to store snacks and extra thermal layers, so I don’t have to open the main compartment during the day when I’m hiking.

The hip belt pockets have waterproof zippers and are large enough to store a small camera, a few food bars, or AquaMira bottles. While I do wish the pockets were positioned a little further forward on the wings of the hip belt so they are more reachable, it’s not a showstopper.

External Attachment and Compression System

The 3400 has a two tiers of side compression straps that can be used to attach gear to the outside of the pack. A bottom compression strap runs horizontally outside each water bottle pocket, while the upper strap is oriented at a diagonal to bring the load closer to the wearer’s back for better load-to-hip transfer.

A Y-strap loops over the top of the pack and is useful for securing bulky items like a foam pad or tent body

In use, I decouple the bottom compression strap over the water bottle pocket because I find it interferes with getting water bottles into the side pockets when I’m wearing the pack (it confuses my hands). Instead, I route the webbing out-of-the-way through additional buckles on the back of the pack which can be used to attach more gear, like snowshoes. HMG sells extra webbing straps for this purpose as an add-on although there’s nothing preventing you from rigging up some cord and cord locks instead.

In addition to the roll top, which provides excellent top compression, there’s a Y strap that runs from the front of the pack (between the shoulders), over the roll top, and attaches on the back of the pack. This strap is great for securing bulky items like a foam pad, rope, or tent body to the top of the pack.

Backpack Frame and Suspension System

Both the Hyperlight Mountain Gear 3400 Southwest Backpack and the 2400 Southwest Backpack have a lightweight frame system called frame stays instead of a rigid wire frame or framesheet made with hard plastic. The stays come preformed but can be easily bent to match your physical characteristics better.

The 3400 has two aluminium frame stays that slot into stay pockets behind the shoulders

The 3400 has two aluminum frame stays that slot into stay pockets behind the shoulders

The frame stays are two aluminum rods that slot into stay pockets on the inside of the main compartment and terminate inside the hip belt. The stays keep the back panel behind your shoulders rigid so it won’t collapse on itself. They also to help transfer some of the pack weight off your shoulders and onto your hips, since the bottom of the stays terminate inside the 3400’s hip belt, which is sewn directly onto all of HMG’s packs. The sewn-on hip belt is one of the main reasons why HMG’s packs carry so well. Shop around. Very few ultralight pack manufactures have a hip belt that is so tightly coupled with the pack body. It makes a huge difference.

The hip belt of the 3400 Southwest is covered with padded mesh, but not overly padded which is what I prefer, with a beefy front buckle for durability. The shoulder straps also have light padding, with sewn-on daisy chains that make it easy to add accessory pockets, like my camera pocket (shown), or navigation devices to the straps.

Daisy chains sewn on the front of the shoulder pads make it easy to attach exra pockets or navigation instruments

When packing the 3400 Southwest, you need to be cognizant of the fact that the pack’s back panel and frame stays end at the top of your shoulders and do not provide extra rigidity for gear stored in the extension collar. Heavy items, like food bags, should be packed towards the bottom of the pack and as close to the back panel as possible. This is doubly important because HMG does not put load lifters on their backpacks because they don’t have full frames (load lifters on frameless packs have marginal utility), and there’s no way to tilt your load forward if you’ve packed it so it pulls your center of gravity backwards.

When I pack the 3400, I put my sleeping bag stuffed in a dry sack at the bottom of the pack and then stack my food bag in top of it, stacking my hammock and other heavy items up the back panel as I go. I stuff lighter weight insulating layers and clothing behind the heavier items to hold them in place, and then put my lightest items in the extension collar (mainly clothing and personal effects). I then use the pack’s roll top to compress the items in the extension collar and shrink the volume they require. This weight and volume distribution provides the best load control since heavy items are located near my hips and there’s a direct transfer of kinetic energy from my core to items located just above the small of my back.

Cold and frosty morning on the Maryland AT with the Hyperlight Mountain Gear 3400 Southwest Backpack

Cold and frosty morning on the Maryland Appalachian Trail with the Hyperlight Mountain Gear 3400 Southwest Backpack

Recommendation

The Hyperlight Mountain Gear 3400 Southwest Backpack is a bomber multi-day backpack geared for tough adventures that will rip most other ultralight-style pack to shreds. It you’re rough on backpacks, but still want one that only weighs two pounds, the 3400 Southwest pack probably has your name on it.

Equally at home on the trail as well as off, the 3400 Southwest Backpack has the extra volume required for longer or more technical trips when you need to carry extra gear or clothing. I use mine for long section hikes on the Appalachian Trail when I need to carry extra food, shoulder season insulation, or cold weather hammocking gear that won’t fit in the smaller volume Hyperlite Mountain Gear ‘s 2400 Southwest Backpack that I use for off-trail hiking and weekend backcountry fishing trips in New Hampshire’s White Mountains.

While highly water-resistant as a benefit of its hybrid cuben fiber construction, the value of the HMG 3400 Southwest Pack lies in its unique combination of low weight and durability without skimping on functional features. You don’t need to compromise on durability if you want a lightweight backpack. A backpack is a big gear purchase. Get one that is designed to last. Nuff said.