Capacity and Volume

Getting a backpack just to have to switch it out mid-trip is a hassle. We recommend buying your backpack last after you’ve collected all of your other gear. You can use a cardboard box to measure the volume of all your gear and then translate the size of that box to cubic inches or liters to determine what pack size you’ll need. Measure only the gear you’ll carry inside of the pack.

ULA Catalyst:

• Total Capacity: 75 liters
• Main Compartment : 43 liters
• Max Carrying Capacity: 40 lbs
• Target Use: Thru-hiking, Large Water and Food Carries, Section Hiking, Winter Backpacking, Bear Canister Carries, Hiking Guides and anyone that carries extra gear for their backpacking partner.

The Catalyst is the largest pack in our line-up and is most utilized by hikers with long stretches between resupply points and heavier loadouts. The Catalyst was designed for carrying a bit more gear, food, or clothing. Its total capacity makes it an ideal choice for longer trips where resupply points are farther apart, like desert sections on the Continental Divide Trail or Pacific Crest Trail. The season you’re considering also comes into play with choosing your pack; hiking in colder weather requires bulkier clothing and gear. Bear country more commonly requires bear canisters and the Catalyst can fit canisters as large as the BV500 horizontally inside of the pack. All of this can add up to be more gear than some other packs can handle comfortably.

ULA Circuit:

• Total Capacity: 68 liters
• Main Compartment: 39 liters
• Max Carrying Capacity: 35 lbs
• Target Use: Thru-hiking, Bear Canister Carries, Section Hiking, Weekend Trips.

The Circuit is slightly smaller than the Catalyst but still offers plenty of volume for multi-day trips. It’s perfect for hikers who have dialed in their gear and don’t need the extra space the Catalyst provides. The Circuit can fit bear canisters as large as the BV500 vertically inside of the pack. The Circuit has been the most popular pack on the Pacific Crest Trail for multiple years in a row and is a perfect blend of a lightweight pack that’s sturdy enough for the demands of a thru-hike.

Pack Weights

• Catalyst: At 44.4 oz for the Robic version and 40.1 oz for the Ultra X, the Catalyst is relatively light for a pack its size, but still heavier than the Circuit due to its larger volume and added support features. Ultra X offers a highly durable ultralight material that provides more weather resistance than the Robic version in a lighter package.
• Circuit: At 37.3 oz for the Robic version and 33.8 oz for the Ultra X, the CIrcuit is noticeably lighter than the Catalyst, making it an excellent choice for those who are looking to cut every possible ounce from their gear. Ultra X offers a nearly 10% weight decrease over the Robic version with added weather resistance.

In summary, if you’re aiming for a truly lightweight nearing ultralight setup, the Circuit might be the better option. However, the Catalyst offers more space and can handle heavier loads, which could be a key consideration for longer trips.

Shared Features

Both the Catalyst and Circuit offer numerous features and external storage options to help keep your gear where you need it.

• Height Adjustable Hip-belt with Pockets: Both packs come with spacious, easily accessible hip-belt pockets for small essentials like snacks, phone, or GPS devices. The hip-belts on both of these packs are removable and height adjustable allowing you to get a more precise torso fit.
• Side Pockets: The Catalyst and Circuit both feature large cinchable side pockets that can easily fit two 1L Smartwater bottles. The Catalyst pockets are a little bit taller than the Circuit side pockets but they both fit the same diameter.
• Shock Cord and Compression Straps: Both models come with shock cord and top + side compression straps to keep smaller loads stable.
• Mesh Dorsal Pocket – Both packs feature a dorsal pocket made up of UltraStretch mesh material. 
• Load Lifters – Both packs feature load lifters that enable you to bring heavier loadouts closer to your body.
• Contoured Shoulder Straps – Both the Circuit and Catalyst are offered in our “S” and “J” style shoulder straps with adjustable sternum strap.
• Hydration Ports – Both packs in the Ripstop Robic Nylon version feature hydration ports to use with a water bladder system.
• Stash Pocket Compatible – Both packs are compatible with our internal stash pocket and water bladder pocket.
• Removable Straps System – All Circuit and Catalyst models built in 2024 or after are compatible with our removable Top Y-strap and removable Bottom Strap systems.
• Top-loading Design: Both packs have a classic top-loading design with a roll-top closure for easy access.
• Ice-axe/Trekking Pole Loops: Both packs feature two points of attachment for ice-axes and trekking poles. A fixed bottom webbing loop holds the ice-axe head in place while a cinchable section of shock cord fastens the handle to the pack near the top of the dorsal pocket.

Where the two differ slightly is in overall storage volume and weight capacity. 

Framing System + Carrying Capacity

Both packs share similar suspension systems but have subtle differences in their frame components..

ULA Catalyst:

• Framing System: Two Internal aluminum frame stays and two layers of dense foam padding in addition to a foam back panel.
• Hip-belt Support: Yes – Removable and height adjustable hip-belt
• Load Capacity: Can carry up to 40 lbs comfortably.

The Catalyst’s suspension system is designed to provide more support for heavier loads, which makes it a better option for longer trips where you’re carrying a lot of food, water, or winter gear. 

ULA Circuit:

• Framing System: A single internal aluminum stay + Delrin hoop and a padded back panel.
• Hipbelt Support: Yes – Removable and height adjustable hip-belt
• Load Capacity: Can carry up to 35 lbs comfortably.

The Circuit features a lighter suspension system, but for loads under 35 lbs, it provides exceptional comfort. If your total pack weight is on the lower end of the scale, the Circuit offers a more streamlined, lightweight option without sacrificing too much in terms of load-bearing comfort.

Bear Canisters

• Circuit:
  • Internal Carrying: Canisters as large as a BV500 can comfortably fit vertically inside of the pack.
  • External Carrying: If your gear is taking up a majority of the space inside of your pack and the bear canister cannot fit, then we recommend the removable Top Y-Strap attachment in order to properly secure your bear canister to the top of your pack.

• Catalyst:
  • Internal Carrying: Canisters as large as a BV500 can fit both vertically and horizontally inside of the pack. We recommend putting your canister in horizontally to get the best fit for your gear.
  • External Carrying: With a pack as large as the Catalyst you’re not as likely to fill up the pack with gear, but if you need to carry a canister on the outside of the pack, we recommend the removable top Y-strap attachment.

Materials

Catalyst:

• 400D Ripstop Robic Nylon – Extremely durable, features a weather resistant coating, heavier than Ultra.
• 400D + 200D Ultra X – The most durable fabric we offer, features highly water resistant laminated backing, the lightest fabric we offer.
• Customizer – You can choose from over 30 fabric options including X-Pac, Ripstop Robic Nylon, ECOPAK, and Cordura,as well as 11 different shock cord colors and 12 different pack panels.

Circuit: 

• 400D Ripstop Robic Nylon – Extremely durable, features a weather resistant coating, heavier than Ultra.
• 400D + 200D Ultra X – The most durable fabric we offer, features highly water resistant laminated backing, the lightest fabric we offer.
• X-PAC – The Circuit is featured in an all X-PAC fabric matrix that features seams on the exterior to make it even more water resistant. Extremely durable and water resistant. 
• Customizer – You can choose from over 30 fabric options including X-Pac, Ripstop Robic Nylon, ECOPAK, and Cordura, as well as 11 different shock cord colors and 12 different pack panels.
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Which One Should You Choose?

Both the Catalyst and Circuit are excellent choices for any backpacker, but the right one for you will depend on your specific trip demands.

Choose the Catalyst if:

• • You need a pack for longer trips (over a week between resupply), thru-hikes, or section hikes.
  • You plan to hike in colder weather and need to carry bulkier gear..
  • You need extra carrying capacity for water carries and longer resupplies.
  • You plan on carrying a large bear canister horizontally inside of the pack.
  • Your total pack weight(Gear + Consumables) is between 35-40lbs.

Choose the Circuit if:

• • You prefer a lighter pack for shorter trips (under a week), thru-hikes, or section hikes.
  • You’ve dialed in your gear to the lightweight/ultralight level and don’t need the extra space.
  • You plan on carrying a large bear canister vertically inside of the pack.
  • Your total pack weight(Gear + Consumables) is under 35 lbs.

Final Thoughts

Both the Catalyst and Circuit are fantastic options for any serious backpacker, offering a great blend of comfort, weight savings, and durability. The Catalyst is better suited for those who need more carrying capacity and plan on longer, more demanding trips where they anticipate a total pack weight that is between 35 and 40 lbs or want to carry a bear canister horizontally inside of the pack. The Circuit, on the other hand, is perfect for ultralight enthusiasts who want to streamline their gear for shorter or less gear-intensive hikes. If you know your total pack weight won’t be over 35 lbs, the Circuit will save you nearly half a pound over the Catalyst!