Rating: 4 / 5
I used this bag on a couple of small hikes followed a 75 miler / 10 day Philmont trek. Once adjusted, it rode quite well. In addition to the main compartment, there are nice sized pockets on the sides, back and belt. The pockets on the belt are very handy for little items you need quickly, be it first aid kit, camera, gps, snacks or other small items.
The volume of the main bag is pretty spacious, allowing for significant stuffing of you sleeping bag and other gear. The construction is quite durable and handles gear compression well. When the main bag was filled, to capacity, we had difficulty getting gear in the side pockets (6 moons lunar solo in 1 side and 2 liter water bottle in the other): The lesson here was to load the side pockets first.
Depending upon our daily trek and food requirements, my Catalyst weight varied between 24 and 40 lbs total.
While ULA recommends this for 30 - 40 lb loads, I would slightly lower that: 40 lbs of gear in my opinion is pushing the limits, both volume and comfortable weight carrying ability, of this pack. At 24 - 30 lbs, this was a *very* comfortable pack, and comfortable up to 35 or 36 lbs. Above that weight, (and I would certainly try to stay under it), I would likely return to my external frame pack.
As delivered with dual framestay (which I recommend for comfort and stability) in a size "large", the delivered weight was 1/2 lb more than advertised on the website, tipping the scales just over 51 ounces. It appeared that the different sizes are not factored into the weight on the ULA Catalyst ordering website when a particular configuration is selected.
Also, it would be nice if there were a couple more attachment loops on the sides at the top of the main compartment side. This would allow for a little easier compression of the main bag or give a couple of more attachment points for items that need to stay close or loose.
Overall, this was a good choice for a larger volume 'ultralight' pack in general, and Philmont is specific, particularly if a degree of ruggedness is required.
It took a couple of weeks longer to receive this pack than stated, but it was worth the weight.