The Hyperlite Mountain Gear Southwest 40 Backpack is a forty-liter backpack (with an additional 9.8L of external storage) that is suitable for ultralight backpacking trips, off-trail hiking through dense vegetation, or winter day hikes when you need to carry extra clothing layers. Made with Hyperlite Mountain Gear’s (HMG) ultralight Dyneema composite fabric (DCF), the pack is outfitted with solid external pockets that are tear and abrasion-resistant for off-trail use in dessert or heavily forested terrain, that would rip mesh pockets to shreds.
Specs at a Glance
- Weight: 1 pound 15 ounces (size large, measured on SH scales)
- Load Capacity: 40 pounds
- Materials: 50D and 150D DCF /Polyester Hybrid and Dyneema Hardline pockets
- Volume: 40L w/ 9.8L of external storage
A Dyneema Composite Fabrics Primer
DCF is an ultralight material used by cottage backpacking manufacturers that is lighter-weight and more rip-resistant than conventional tent and backpack fabrics. Tents or backpacks made with DCF are often half the weight of those made using high-tenacity nylon or polyester, making it an attractive material for hikers and backpackers looking to slash their gear weight without loss of functionality or capacity.
More technically, DCF is a non-woven, laminate fabric made using ultra-high-weight-molecular polyethylene and polyester that produces an exceptionally strong and waterproof material. It’s also more expensive to manufacture than conventional fabric because gear manufacturers have had to evolve manual fabrication and styling processes (gluing and taping in addition to sewing) to create products using it. That price is unlikely to go down because DCF products are too expensive to produce in large quantities.
The Hyperlite Mountain Gear Southwest 40 Backpack reviewed here is constructed from a hybrid DCF and polyester sandwich, with DCF on the inside with a protective layer of 50 denier polyester or 150 denier polyester on the outside for high wear areas. The outer layer gives it even more strength, prevents fraying, and provides better long-term protection against the decaying effects of ultraviolet light.
Internal Storage and Organization
The HMG Southwest Backpack 40 is laid out in a traditional ultralight style with a large main compartment, side water bottle pockets, and a large front pocket. With 40 liters of internal closed capacity, the Southwest is the smallest volume overnight pack in the HMG product line.
The main compartment has a drybag-style closure system with velcro around the edge to facilitate closing the top before rolling it shut. There’s a hydration loop on the interior of the back panel with an internal mesh pocket that can be used to suspend a hydration reservoir, with a single hydration port located on the right side of the pack.
There are five external pockets on the Southwest 40, two side water bottle pockets, a larger center pocket, and two hip belt pockets. All of the pockets are made of solid 210 denier Dyneema Hardline (reinforced nylon), enabling the pack to be used in off-trail conditions that would quickly shred mesh pockets or abrade the lighter-weight DCF hybrid used throughout the rest of the pack.
The side water bottle pockets are large enough to fit 1-liter water bottles together with tall skinny items like tent poles or an ultralight fishing rod and have drain holes at their base. The pockets are reinforced at the base to prevent punctures or tearing. Water bottles stored in the pockets are also reachable and replaceable while wearing the pack, a must-have in my book.
The larger center pocket is open at the top and sized for carrying extra layers, a small cooking system, or wet items like a water filter.
Finally, while the hip belt pockets on the Southwest 40 are large enough to hold several food bars or a small camera, I mainly use them to store small items that I use frequently during the day like Aquamira drops, my compass, suntan lotion, or a bottle of DEET for when the bugs get bad.
The hip belt pockets on the Southwest 40 are also made using 210 denier Dyneema reinforced nylon. This is crucial for off-trail travel where you lead with your hips through thick vegetation.
From a capacity standpoint, you can carry 1-2 nights of gear and food in the Southwest 40 if it’s very compact, but if you need to carry more food between resupply stops, you should size up to a larger capacity model like the Southwest 55 Pack.
External Attachment Points and Compression System
The Southwest 40 has two tiers of side compression straps that can also 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.
Additional top-down compression is provided by a dry bag style top closure which is rolled down to “use up” any extra volume. The side clips of the roll-top closure can be clipped down along the sides of the pack attaching to vertical webbing straps, while a top Y strap provides additional top compression and a place to secure an external sleeping pad or climbing rope (see Backpacking External Attachment Guide: How to Carry Gear on the Outside of a Backpack.)
Alternatively, the side clips can be clipped to one another on top of the pack bag, and the two vertical webbing straps can be clipped together above the large center pocket, providing an excellent way to secure snowshoes to the back of the pack for winter travel. This is a very nice feature that winter hikers will appreciate.
There are also four small tri-glide buckles sewn on the outside perimeter of the center pocket which can be used to secure additional gear such as a crampon pocket or climbing helmet using webbing straps. HMG sells these as an add-on purchase.
Backpack Frame and Suspension
The HMG Southwest 40 Pack is basically a frameless rucksack that comes with two optional aluminum stays that help keep the pack from collapsing on itself when you load it up with gear. For a pack of this size, that’s all you really need in terms of structural support since the Southwest 40 doesn’t have enough capacity to carry a really heavy load.
The two aluminum stays run vertically down channels inside the main compartment, terminating in the hip belt of the backpack which is sewn to the base of the pack. This direct kinetic attachment system provides superior load-to-hip transfer, something that HMG packs are known for.
Basically unpadded, the hip belt molds easily around your hips, even square hips, while the spacer mesh lining wicks away moisture. Personally, I prefer less padded hip belts on lightweight backpacks because I think I get a better fit, but you also don’t need all that extra padding since this is such a small pack and you can’t go that heavy with it.
Comparable Ultralight Backpacks
|Make / Model||Volume||Weight|
|Gossamer Gear Gorilla Backpack 40L||40L||30.5 oz|
|Hyperlite Mountain Gear Southwest 40||49L||30 oz|
|Northern Ultralight Sundown 46||46L||28.5 oz|
|Waymark Gear Lite||50L||29 oz|
|Superior Wilderness Designs Superior 40||48L||15 oz|
|Superior Wilderness Designs Rugged Long Haul 35L||45L||29 oz|
Designed specifically to prevent snags in the rough scrub brush of America’s deserts, the Hyperlite Mountain Gear Southwest 40 is built bomber tough for short multi-day backpacking trips with frequent resupplies. Equally at home on the trail as well as off, this lower-volume pack also makes an excellent day hiking or winter pack for more technical trips when you need to carry extra gear or clothing.
While the Southwest 40 Pack is surprisingly heavy at 31 ounces for a DCF backpack compared to other ultralight packs, keep in mind that this pack is purpose-built for off-trail travel. For example, the Southwest 40 uses solid fabric panels for external pockets instead of mesh, which would get quickly get ripped to shreds, or lighter-weight DCF, which abrades when repeatedly brushed up against hostile vegetation.
While highly water-resistant as a benefit of its DCF construction, the value of the HMG Southwest 40 Pack lies in its unique combination of low weight and durability without skimping on functional features. If you need a backpack that can go through off-trail hell and high water, the HMG Southwest Pack 40 is your ticket.
- Taped seams and needle holes make the pack nearly waterproof
- White color makes it easy to find gear inside pack
- Roll top closure and side straps provide good compression
- Side water bottles are reachable and replaceable while wearing the pack
- Bomber tough against puncture or abrasion by aggressive vegetation
- Side and front external pocket have reinforced bottoms and drain holes
- Fantastic load to hip transfer
- Daisy chains sewn into shoulder straps make it easy to attach accessories
- Good range of sizes available for people with short torsos, including women
- Center ice axe loop is awkward to use; no shaft attachment provided
- Mfg stated 40 pound max load rating is generous
Disclosure: HMG donated a backpack for review.SectionHiker is reader-supported. We only make money if you purchase a product through our affiliate links. Help us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.