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Since debuting in 2001, ULA (Ultralight Adventure Equipment) has been a prominent force in the long-distance hiking community. ULA describes the Catalyst as a “tried and true workhorse,” and we would have to agree wholeheartedly. This pack weighs considerably less than most of the competition, fitting easily into the weight range of our lineup of ultralight backpacks, yet comfortably carries loads as well or better than many of the fully-featured packs we tested. The features, while simple, are extremely user-friendly and made in a way to reduce excess weight. Anyone who considers themselves a lightweight backpacker, but wants the ability to carry a little more weight from time to time, will love this pack. This may not be the most innovative or high-tech backpack in our test, but ULA sticks with the basics with the useful and comfortable Catalyst. Compare it to top competitors in our backpacking backpacks review.
REASONS TO BUY
Lightweight
Comfortable
Supportive
Functional feature set
REASONS TO AVOID
No lid
Back panel lacks ventilation
Minor Updates for 2025
While the core of this pack remains the same, ULA has made some minor improvements and additions to the Catalyst — and all their packs — including:
New more durable mesh (claimed) for the front pocket
Ice axe / trekking pole loops are now a standard feature
Loops on top and bottom to attach optional Y straps that can be purchased from their website
This comfortable yet supportive pack has an extremely functional set of features and is one of the lightest in our test
This super-light pack caries loads like a pro and has just about every feature you could ever want
This now classic pack offers incredible ventilation, an awesome set of pockets, and a hug-like suspension
The Flash 55 is a great value, with excellent features and a great weight to volume ratio at an affordable price
This heavier but more comfortable pack provides great support for larger loads
Rating Categories
Ultralight Adventur...
Granite Gear Blaze 60
Osprey Atmos 65 AG
REI Co-op Flash 55
Osprey Aether 65
Comfort(40%)
8.5
9.0
10.0
8.0
9.0
Ease of Use(25%)
8.0
9.0
8.0
8.0
8.0
Weight-to-Volume Ratio(20%)
10.0
8.0
5.5
9.0
5.0
Adjustability(15%)
5.0
8.0
8.0
7.0
9.0
Specifications
Ultralight Adventur...
Granite Gear Blaze 60
Osprey Atmos 65 AG
REI Co-op Flash 55
Osprey Aether 65
Measured Weight
2.8 lb
3.0 lb
4.6 lb
2.8 lb
5.0 lb
Advertised Volume
75 L
60 L
65 L
55 L
65 L
Weight per Liter
0.60 oz/L
0.80 oz/L
1.13 oz/L
0.81 oz/L
1.23 oz/L
Organization Compartments
Front mesh pocket, side water bottle pockets, hip belt pockets
Lid, front mesh pocket, side water bottle pockets, hip belt pockets
Lid, front mesh pocket, side water bottle pockets, hip belt pockets
Lid, front mesh pockets, 2 side pockets per side, hip belt pockets, shoulder strap pocket
Lid, front pocket, side water bottle pockets, hip belt pockets
Access
Top
Top, front
Top, sides, bottom
Top
Top, front, bottom
Hydration Compatible
Yes
Yes
Yes
Yes
Yes
Sleeping Bag Compartment
No
No
Yes
No
Yes
Materials
400 Robic fabric
100D robic nylon w/ DWR coating
Main Body: Recycled 210D honey comb nylon
Accent: Recycled 210D high tenacity nylon
Bottom: Recycled 500D high tenacity nylon
Main Body: 100D ripstop nylon
Bottom: 420D nylon
420HD nylon, DWR treatment
Measured Volume (main compartment)
55 L
58 L
50 L
45 L
45 L
Our Analysis and Test Results
The Catalyst is, far and away, one of the lightest weight packs that can comfortably carry a moderate load. Despite this low weight, it still has enough features to continually remain one of our favorite packs.
The ULA Catalyst has everything a long-distance hiker wants in a pack.
Credit: Elizabeth Paashaus
Comfort
The Catalyst is the workhorse of the ULA line. The recommended max weight is 40 pounds, but we found that to be slightly conservative. We tested this pack with over 45 pounds, and it performed admirably. Whether you are loading this pack with heavy climbing gear or crammed full with a fresh resupply out of a trail town, this pack can take the weight.
The suspension consists of a frame sheet and two (malleable) aluminum stays that transfer load weight to the comfortably padded hip belt. While this style of frame is dated, it still does a great job of redistributing weight off your shoulders and onto your hips. The shoulder straps are padded well and come in the standard J-Straps and S-Straps to fit different body types. The mesh-style foam back panel doesn't breathe as well as a more modern trampoline-style harness, but it is comfortable on your back and dries quickly after a sweaty hike.
The roll-top takes some getting used to if you are accustomed to a cinch top with a lid, but getting a good closure is a piece of cake.
Credit: Elizabeth Paashaus
Ease of Use
The Catalyst is loaded with incredibly functional features. It's no wonder ULA rarely changes things up with its line of backpacks. Some of our favorite features include huge side pockets, an excellent front mesh stuff pocket, dual-zippered hip belt pockets, and a front shock cord lashing strap. These features are not revolutionary, but they are undeniably user-friendly.
The large side pockets can hold two tall Smartwater bottles each for those long desert crossings with limited water, but they are useful for much more than just bottles. We found that we could fit rain gear or a pack cover in addition to a single tall bottle. An adjustable shock cord helps keep everything in the pockets contained and secure. The pockets also angle forward, so it is easy to reach back with one hand to remove and reinstall the bottles on the go without taking off the pack.
With huge side pockets, this pack can easily carry up to six liters of water (with the use of the internal water bladder sleeve). No desert trail is too long or dry for this pack.
Credit: Elizabeth Paashaus
The Catalyst is advertised as a 75-liter pack. However, it is worth noting that the main compartment is only listed as 43 liters. To account for the remaining capacity, ULA includes the side pockets, the exterior collar, the hip belt pockets, and the stretchy mesh pocket. From our experience, this pack doesn't feel as large as most other 75-liter packs.
The front mesh pocket is another perfectly executed feature. This pocket is huge, encompassing most of the front of the pack, and is an ideal place to stuff light layers, a pack cover, fuel bottles or canisters, and just about anything stuffable that will fit in this large 10-liter capacity pocket. Any bulky layers that won't fit in the stuff pocket can easily be strapped to the front of the pack using the shock cord lashing. This is also an ideal place for a closed-cell foam pad or drying wet socks, bandanas, or underwear.
The shock cord on the front of the mesh pocket can accommodate a huge variety of gear.
Credit: Elizabeth Paashaus
Having exceptionally large and accessible hip belt pockets, they are useful and versatile. We found them perfect for our phones, snacks, map & compass, water treatment, chapstick, and any wrappers or trash found on the trail. The roll-top takes a little getting used to since it has to be buckled on each side, but the simplicity of not having the top lid makes up for the minor inconvenience. However, closing the pack when loaded all the way to the top feels slightly less secure until the top compression strap is fastened and tightened.
Large hip belt pockets hold all the small on-the-go items like snacks, phone, or a map and compass.
Credit: Elizabeth Paashaus
Weight-to-Volume Ratio
We were blown away by how light this felt when empty. Weighing just under 3 pounds, the Catalyst is an incredibly lightweight pack that performs extremely well, even when loaded with over 40 pounds of gear. Though some other packs we tested weigh about the same, the Catalyst's higher volume gives it a very impressive weight-to-volume ratio that more than makes up for a few extra ounces.
The true minimalist will also love that this pack has multiple removable features (hydration sleeve, hand straps, shoulder strap water bottle keepers, and small internal storage sac). Depending on what configuration you decide, the total weight can be reduced by up to four ounces. The 400 Robic fabric used on this pack is durable and tear-resistant, yet lightweight. The Catalyst also saves weight by keeping the suspension and construction simple.
Adjustability
With four harness sizes available, regardless of your torso size, it's almost guaranteed that there's a Catalyst that will fit. They range in torso length accommodation from 15 to 24 inches. They also offer six separate hip belt sizes to fit a wide range of waist measurements, from 26 to 47 inches.
Finally, they offer two types of shoulder strap shapes: the J-Curve and the S-Curve. J-Curve is their original and works best for most men, but men with certain body types (athletic build) will benefit from the S-Curve. While each pack only has a small amount of adjustment, each size accommodates about four inches of torso lengths, and with some up-front planning, a great fit is easy to get.
Compare the S-curve shoulder strap (left) to the J-curve (right).
Credit: Adam Paashaus
Should You Buy the Ultralight Adventure Equipment Catalyst?
If you want a comfortable pack that carries heavy loads well, is impressively lightweight for its volume, and has a great set of features, then the ULA Catalyst is a solid choice. This pack is super light for the amount of weight it can carry comfortably and has useful features for long-distance hiking. If you're on a tight budget, this backpack may seem expensive, considering how simple it is. But for those who want a large carrying capacity, and value-saving weight without sacrificing pocket options, we think this pack is worth the cost.
What Other Backpacking Backpacks Should You Consider?
The time-tested ULA Catalyst is an ideal pack for long-distance hiking — it's lightweight, comfortable, and scales up and down depending on how much food and gear you're carrying. If you're looking for a pack with a few more features, like a top lid and front-panel accessibility, check out the Granite Gear Blaze 60. Check out the Deuter Aircontact Core 65+10 for the most organization and accessibility of any pack we tested. If you're looking for a backpack with a more supportive, breathable, and comfortable back panel, consider the Osprey Atmos 65 AG or Osprey Exos 58.
At the northern terminus of the Long Trail on our thru-hike. The LT was no easy walk in the woods.
