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ULA Catalyst 75L Backpack Review

ULA Catalyst Backpack Review

The ULA Catalyst Backpack is the largest volume backpack in ULA’s line of ultralight style packs with 75 liters of capacity. Weighing 44.4 oz (1259 g), it’s a durable backpack that can carry an enormous amount of gear and food, packed inside its main compartment or lashed to the exterior. I affectionately refer to it as the “U-Haul of the ULA product line because it can carry so much. That said, the Catalyst is a great lightweight pack option for people who plan to take extended trips into the backcountry and need a pack that can carry a lot of extra food or water, a bear canister, cameras, fishing rods, and technical equipment in addition to your normal backpacking gear. It’s also an excellent pack for professional guides who need to bring extra equipment.

Specs at a Glance

  • Total Volume: 4,600 cu in /75 liters (49 liters in main + extension collar)
  • Rec’d Max Load: 40 lbs
  • Pockets: 5 + Main
  • Load Lifters: Yes
  • Hydration Compatible: Yes (reservoir pocket sold separately)
  • Bear canister compatibility: BV500, BV475BV450BV425 (all fit horizontally and vertically)
  • Fabric: 400d Robic nylon (multiple colors available)
  • Torso Lengths: 15-18″, 18-21″, 21-24″, 24″+
  • Hip Belt Sizing: 26-30″, 30-34″, 34-38″, 38-40″, 42-47″, 47″+
  • Gender: Men’s and Women’s-specific shoulder straps available.
  • See ULA’s Catalyst Product Page for Complete Specs

Backpack Pockets and Organization

The Catalyst is a roll-top with side bottle pockets and a large front stretch pocket.
The Catalyst is a roll-top with side bottle pockets and a large front stretch pocket.

The ULA Catalyst is laid out like a standard ultralight backpack with a rear mesh pocket, side water bottle pockets made with solid fabric, and a single tier of side compression straps. It’s a roll-top pack (without any top snaps, velcro, or a stiffener) that can be secured to the sides of the pack with straps and buckled together on top. If the latter, the extra straps can be looped around the backpack to provide rear compression or act as an attachment point to lash gear to the outside of the front mesh pocket, which can be very handy if you need to carry large objects like snowshoes. There’s also a piece of webbing that runs over the roll top from between the shoulders to the top of the rear mesh pocket, providing additional top compression for keeping the load under control.

Rather than being square, the bottom of the pack rounds inward instead of having a square bottom in order to bring the heaviest items, typically placed at the bottom or middle of your pack, close to your lumbar back area where they can be carried most efficiently. Clever design.

The bottom of the pack is curved not square
The bottom of the pack is curved not square.

The side water bottle pockets are solid, not mesh, to protect them from abrasion and tearing. They’re also quite large and you can fit 2 x 1-liter bottles in each side. Both water bottle pockets have drains at their base. The top of each pocket has an elastic cord that can be cinched closed and secured with a cord lock to keep items from shifting or dropping out. Tall skinny bottles are easier to reach and replace than short wider ones, like 1L Nalgenes.

The front of each side pocket has a small hole you can stick your hand into although that’s not the intention; it’s part of the shoulder strap suspension system which terminates at the base of each pocket. But be forewarned, small items can fall out of the side water bottle pockets and shouldn’t be used for that type of storage.

The shoulder straps are anchored inside the side pockets
The shoulder straps are anchored inside the side pockets.

Like many ultralight style packs, the Catalyst has a full-length front mesh pocket that’s ideal for storing wet gear or layers you want fast access to during the day without having to open up the pack’s main compartment. The mesh is very fine and heavy-duty so it won’t snag on protruding items or tear. I typically store my rain gear, water filter, and an empty wet reservoir in the mesh pocket when I hike, or a wet rain fly, so I can pull it out easily to dry during rest stops and keep it away from my dry clothing inside the main compartment.

The hip belt pockets are large with solid exteriors for durability
The hip belt pockets are large with solid exteriors for durability.

Finally, there are two large zippered pockets on the exterior of the hip belt, large enough to store a hat and gloves, a smartphone, a camera, snacks, Aquamira bottles, bug dope, and such. The fronts of both pockets are hard-faced to prevent tearing with heavy-duty zippers for durability.

Backpack Frame and Suspension System

The frame, shoulder strap, and hip belt customization options on the Catalyst and ULA’s other packs are what sets their packs apart from most off-the-shelf backpacks you can buy at retail stores. In addition to 4 torso sizes ranging from 15″ to 24″ and 6 hip belt lengths ranging from 26″ to 47+”,  you can further refine the sizing and fit of the Catalyst in several important ways to get an even more personalized fit.

The frame consists of two foam sheets glued together
The frame consists of two foam sheets glued together.


The ULA Catalyst has a fairly beefy frame as ultralight style packs go, with two foam pads that are glued together and two aluminum stays oriented in a V-shape that terminate in front of the hip belt. The pads and stays are tucked away in a zippered internal pocket and are accessible, but they can’t be used conveniently for multiple purposes, like as a sit pad, and I’d leave them alone.

The rear foam panel has frame stay pockets which contain aluminum stays
The rear foam panel has frame stay pockets that contain aluminum stays (rear view).

The aluminum stays are pre-shaped when you receive the pack and will work as-is for most people, but can be removed and bent further for a custom fit. You can’t do this with most off-the-shelf backpacks or ones that don’t use a stay system. Bending frame stays can significantly enhance the fit of a hip belt if you find that it slips constantly or give your head more clearance if it touches the top of your pack. (See also: How to bend backpack frame stays).

If you need to carry the largest Bear Vault 500 bear canister, it will fit horizontally in the Catalyst and the frame stays and foam pad of the frame will protect you from feeling its hard edges. That said, I find it much more comfortable to carry a BV500 vertically and to pack my gear around its sides. When positioned horizontally, the BV500 causes the sides of the pack bag to stretch tightly, pulling the shoulder straps apart which can cause discomfort. While you can carry the canister horizontally in a pinch, it’s just not terribly comfortable despite the foam-padded frame.

S-shaped shoulders straps are available as an option.
S-shaped shoulder straps are available as a free option.

Shoulder Straps

Like ULA’s other backpacks, the Catalyst is available with traditional male (J-shaped) or female-friendly (S-shaped) shoulder straps…although a lot of men prefer those S-shaped straps as well. I requested them on this pack to show you what they look like. The S-Shape is good for people with sloping shoulders or well-developed chests and can help make the sternum strap (which slides up and down on a webbing strap) more comfortable. ULA packs are very popular with women backpackers for this reason.

In addition to load lifters, the shoulder straps have front load lifter adjustments, which slide down the front of the shoulder pad to let you adjust the angle of your load lifters if they’re too flat (a 45-degree angle is ideal). Most of these shoulder pad options are usually only found on a high-end expedition or custom packs costing much more than the Catalyst.

The hip belt can be repositioned up to 2 inches higher shortening the torso length.
The hip belt can be repositioned up to 2 inches higher shortening the torso length.

Hip belt

The hip belt is available in multiple lengths independent of the torso length of the backpack, making it possible to get a near custom fit. The hip belt is held in place with velcro on the front and back where it runs through the pack frame.

If you want to fine-tune the torso length of your Catalyst, you can raise or lower the hip belt by about 2″ by unsticking the velcro and moving it up or down, adjusting the torso length in the process. Reconnect the velcro – it holds solidly – providing yet another way to really dial in a personal fit with the ULA Catalyst. I never really appreciated this feature on ULA packs until I used it on the Catalyst. It made a big difference in load-to-hip transfer when I had to carry a lot of heavy gear and getting the right torso length was critical.

The two tiered hip belt can be adjusted to fit your hip shape.
The two-tiered hip belt can be adjusted to fit your hip shape.

The Catalyst hip belt is quite wide and has two interlocking straps on each side that let you tension the top and bottom half of the belt to fit your precise body dimensions The top and bottom straps on the hip belt are actually one strap (if you make the top longer, the bottom gets shorter). I usually make the top strap tighter than the bottom, to prevent the hip belt from slipping down over my hip bones. I think the ULA Catalyst backpack has the best hip bet available today amongst ultralight pack makers in this weight class in terms of fit, comfort, and load transfer. It rides securely and comfortably over your iliac crest and won’t slip even if you have a heavily loaded pack. Note: The Catalyst hipbelt is the same on the ULA Circuit and ULA Ohm backpacks.

The sides of the hip belt also have what are called hip control straps that pull the base of the pack bag closer to your back and help dampen lateral sway when scrambling. This is important for a high-capacity backpack like the Catalyst to help reduce momentum that can make you lose your footing and tumble when carrying a heavy load.

External Attachment and Compression System

The Catalyst has two primary mechanisms for compression, the roll top w/ top webbing strap for squishing your load down vertically, and a single tier of side compression straps for pulling gear in the main compartment closer to your back and core muscles. When fully loaded, carefully balancing the weight inside the pack and pulling the side compression straps tighter results in an easier carry. At 75L, the Catalyst has a larger capacity than most ultralight style packs, and pack compression becomes more important than on smaller volume packs.

The Catalyst has one tier of side compression straps
The Catalyst has one tier of side compression straps.

In practice, I’ve also found it easy to store long items such as fishing rod tubes and umbrellas in the side water bottle pockets together with a water bottle, using the one compression strap to keep the longer items secured against the side of the pack. But the side pockets are so large, that you can store much bulkier items in them like a one-person tent rolled up (held in place with the top compression strap), although I’d recommend balancing the weight on the other side of the pack with something that’s equivalent in weight.

ULA Catalyst 75L Backpack


High Capacity U-Haul

If you're looking for a lightweight backpack that can still carry a lot of gear, the Catalyst is for you. It's a very comfortable and durable backpack with an amazing hip belt that makes heavy loads feel lighter.

Shop Now

One area where the Catalyst is very strong is the ability to attach gear to its shoulder straps. This is great on wilderness trips where you want to keep electronic devices or map cases within easy reach. The shoulder straps come with two plastic rings that you can clip items to and there are some daisy chain loops below the sternum strap on both sides.

It’s easy to add pockets or electronics to the shoulder straps.
It’s easy to add pockets or electronics to the shoulder straps.

In addition, there are trekking pole holders (top and bottom) on both sides of the front mesh pocket that can also be used to carry an ice ax.


The ULA Catalyst is available in a wide range of colors and in Robic Nylon, XPac, or Ultra.
The ULA Catalyst is available in a wide range of colors and in Robic Nylon, XPac, or Ultra.

The 75L ULA Catalyst is one of the largest ultralight style backpacks that you can buy that weighs less than 3 lbs. It’s ideal for backpackers who need a high-capacity backpack to carry a lot of extra gear or supplies into the backcountry but want a minimalist-style backpack that is all-function with little extraneous fluff. Like ULA’s other packs, the Catalyst is available with a wide variety of torso lengths and hip belt sizes, so you can get a great fit, with additional capabilities that let you tune the fit to your personal dimensions – really an essential when carrying heavier loads. The Catalyst is also a durable and proven pack for tough trips, one that’s earned near legendary status among guides and backcountry adventurers. ULA also offers a huge number of customization options on the Catalyst from colors and fabrics to extra straps to attach gear to the outside of the backpack. An even more abrasion-resistant XPac or  Ultra 24 Catalyst is also available.

See also:

ULA Equipment-Free Shipping on all US Orders
Disclosure: ULA loaned the author a Catalyst backpack for this review.

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  1. It carries the weight well when you need to pack winter gear and/or food for a week. The hip belt pockets are big enough to carry lunch and snacks for the day, plus sunscreen and maps. And like Philip, I use the big mesh pocket for raingear and water related gear. So, I rarely have to open the main compartment before the next campsite.

  2. Hi
    Pack makers are extremely low on knowledge on how to calculate pack volumes and always(?) end up with vastly exaggerated numbers.
    It would have been interesting to know how this pack compares to a 3400 series HMG pack – how the main pack volumes compare that is.
    And 40 lb. seems a bit low, food water and tech are heavy to carry.
    Thanks for all the great info, Einar

    • They also use different metrics for which pockets “count” in the total. This is a high-volume pack though. You can see their pocket volume breakdowns on their website as well, since they are very transparent in their calculations.

  3. Still waiting for an ultralight 90L. Waiting, waiting, waiting. One day, maybe.

  4. This pack is a workhorse! I took it out for three weeks of backpacking in Yellowstone and Wind River areas in July. Pack held up great and carried the weight well consistently having loads at or near 40 lbs. So many different options to pack it up with the giant size pockets. Highly recommended for trips where you may need extra food, water or miscellaneous gear.

  5. How does the usable volume / packability of the Catalyst compare to the HMG 3400 Southwest?

    I ask because the numbers are a bit confusing. On paper, the Catalyst has 75L and the 3400 has 64.5L total capacity. However, there is less room in the main storage area of the the Catalyst (2600 main + 600 extension = 3200 cu in) than the 3400 cu in of the Southwest. The main difference is the claimed volume of the side, mesh, and hipbelt pockets (22.6L Catalyst, 9.5L Southwest).

    I am less concerned with the published number given the lack of standards, and more interested in your experience and thoughts with packing and carrying volume in both packs. Thanks!

    • The Catalyst is much easier for me to use than the Southwest. I like to carry a lot of gear outside of main compartment and the pockets on the Catalyst are deeper and have better security for this purpose. I’ve also lost a lot of gear from the Southwest’s side pockets over the years from water bottles to fishing rods. Stuff pops out. The hip belt pockets are also nowhere as good as the ones on the Catalyst. Hope that answers your question.

      • Yes. It answered my question. Thanks for sharing your experiences with the Catalyst and Southwest! I appreciate your insights and reviews!

  6. I tried a Catalyst almost 5 years ago, and had it custom fit at an authorized retailer. I tried it on a number of 6-mile practice hikes in town, and found it very uncomfortable compared to my standby Deuter. Ended up returning it. Has the Catalyst changed that much since then? I’m now using a Deuter Act Lite 60+10, but hoping to find something lighter for the 5 & 6 day trips we’re doing in Wind River Range and Sierras this summer. My 72-year old body would appreciate a lighter pack. Thanks!

  7. What is the heaviest load any of you have carried in the 75L Catalyst and how “comfortable” did it feel at that weight? Thanks for your help.

  8. 40 lbs. It felt fine to carry 40 lbs…ULA packs tend to feel the same regardless of how much weight you put into them.

    • I’ve had a Catalyst for about 10 years. I’m typically in the Grand Canyon in February and dry camps are part of the game. Sleeping on the rim of the Inner Gorge while on the Tonto Plateau is incredibly scenic, well worth hauling a few liters of water for a few miles. That water often pushes my load into the 40lb. range. I never felt I was maxing out the Catalyst.

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