The ULA Catalyst Backpack is the largest volume backpack in ULA’s line of ultralight style packs with over 75 liters of volume. Weighing 44 -48 ounces (depending on configuration), 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 “moving van” 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, cameras, or technical equipment in addition to your normal backpacking gear. It’s also an excellent pack for professional guides who need to bring extra equipment or carry their clients’ loads when they need a little extra help.
Specs at a Glance
- Total Volume: 4,600 cu in /about 75 liters
- Rec’d Max Load: 40 lbs or less
- Rec’d Base Weight: 20 lbs or less
- Fabric: 210d Robic standard, or 500d Cordura available
- Torso Lengths: 15″-24″
- Hip Belt Sizing: 26″-42″
- Gender: Men’s and Women’s-specific shoulder straps available.
- See ULA’s Catalyst Product Page for Complete Specs
Main Compartment and Storage Capacity
The ULA Catalyst an ultralight style roll-top backpack with a large main compartment, rear stretch mesh pocket, and large side water bottles pockets, with large zippered pockets on the hip belt. Several optional interior pockets come with the pack for storing a hydration reservoir (there are two hydration ports on the sides) or personal effects but can be non-destructively removed with the plastic clips that hold them in place.
The main compartment is enormous with a long extension collar. It closes with a roll top, that’s clipped to webbing straps attached along the sides of the back panel below the shoulders. When the top is rolled close, the position of these webbing straps helps pull the load forward over your hips for maximum load transfer. 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 of your pack, as close to your lumbar back area where they can be carried most efficiently. Clever design.
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, easily reachable while wearing the backpack. Both water bottle pockets have drains at their base and are covered with solid 210d Robic Nylon fabric for extra durability, including reinforced pocket bottoms. 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. If you habitually rip up mesh water bottle pockets, these should keep you out of trouble.
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.
Like many ultralight style packs, the Catalyst has a full-length rear 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 shelter, so I can pull it out easily to dry during rest stops and keep it away from my dry clothing inside the main compartment.
Finally, there are two large zippered pockets on the exterior of the hip belt, large enough to store a hat and gloves, a camera, snacks, Aqua Mira bottles, bug dope, and such. The fronts of both pockets are hard faced to prevent tearing with heavy-duty zippers for durability.
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 for comfort and carry efficiency than on smaller volume packs.
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 water bottle pockets are so large, you can store much bulkier items in them like a two-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.
Having just one pair of side compression straps makes it a bit difficult to secure a pair of snowshoes to the sides of the backpack over the water bottle pockets (two straps are preferable). Snowshoes weigh 5 pounds per pair, making them one of the heaviest and most awkward items you might carry on a backpacking trip. While you can secure snowshoes under the elastic strap over the rear mesh pocket, there’s nothing stopping you from rigging up your own ad hoc side compression straps using cord and cordlocks between gear loops on the outside of the water bottle pocket and the perimeter of the rear mesh pocket. You just need to be a little creative.
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 front of the Catalyst’s shoulder straps have daisy chains attached to them, plastic gear loops, and four elastic water bottle holders (the latter are also easy to remove nondestructively.) Want to attach an umbrella to your shoulder straps? It’s quite easy with the rich set of shoulder strap attachment points provided on the ULA Catalyst backpack.
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 5 hip belt lengths ranging from 26″ to 42+”, you can further refine the sizing and fit of the Catalyst in several important ways to get an even more personalized fit.
The ULA Catalyst has a fairly beefy frame as ultralight style packs go, with two interior foam panels and two aluminum stays that terminate in the lumbar pad that holds the hip belt in place.
The foam panels are used to keep angled objects from poking through the pack bag and int0 your back. The rear panel holds two pre-shaped aluminum stays (flat-sided metal rods) that terminate in the lumbar pad of the hip belt behind the small of your back. They do most of the work in transferring the load to your hips.
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 don’t use a stay system. If you’ve never bent frame stays before, I recommend you contact ULA customer support for expert advice on how to go about doing it or undoing it, if you botch it up. 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.
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 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 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. But hip belt fit is a very personal thing that can be affected by your dimensions, how much body fat you have on your hips and the curvature of your lower back. Experiment and contact ULA for fitting advice if you need it. They’re very responsive on fit issues.
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 step and tumble when carrying a heavy load.
Both the hip belt, back panel, and shoulder straps are covered in padded spacer mesh which is cushy without being too soft. The holes in the spacer mesh have a tendency to collect debris like spruce or pine needles however if you wander off-trail.
The Catalyst’s shoulder straps are available in two styles, J-shaped or S-shaped, to accommodate people with breasts or barrel chests. Ladies, S-curved shoulder straps are better than the so-called “unisex” shoulder straps provided by other pack makers. ULA is one of the few lightweight pack makers that provide features and sizing that are tuned for a female fit, something to seriously consider if you plan to wear a backpack for the six months at a time, especially if you need to haul more gear in a pack that’s the size of the Catalyst.
In addition to the numerous attachment points (discussed above), 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 ULA Catalyst is one of the largest sub-three pound ultralight style backpacks that you can buy with 75 Liters of carrying capacity. It’s ideal for more experienced 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’s all function with little extraneous fluff. Like ULA’s other packs, the Catalyst is available with a wide variety 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.
While the Catalyst can be used by backpackers transitioning from more traditional gear and a heavy pack to a lighter one, I would encourage you to look at the 68 liter ULA Circuit backpack if most of your trips are going to be four days or less. The Catalyst is a high-capacity backpack that is really best used for larger loads and longer trips. While the two packs are very similar and can even be difficult to tell apart for the untrained eye, the Circuit is a better-sized pack to get if you intend to further reduce your load and gear volume over time. For more information about the ULA Circuit, read my review.
Disclosure: ULA loaned the author a Catalyst backpack for this review.Editor's note: Help support this site by making your next gear purchase through one of the affiliate links above. Click a link, buy what you need, and the seller will contribute a portion of the purchase price to support SectionHiker's unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.
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