I’ve had a handful of multi-day packs. So far, I’ve carried the Osprey Atmos AG 65 and Exos 48, Deuter Aircontact 65, and Teton Sports Explorer the longest. The former three are great long distance packs, while the Teton is my sturdy bushwhacking-in-thorns pack. All three are a little on the heavy side, ranging from three to six pounds. I like that feeling of my pack being glued to my back, so I don’t mind the extra weight.
I’ve also carried lighter packs, having borrowed a 40L HMG Junction 2400 and a 50L Six Moons Minimalist, but ultralight packs have never been my cup of tea. This preference comes down to one feature: Back panels.
It’s less about the weight carried, to me. Most packs feel good when properly loaded with the appropriate load. It’s all about heat and sweat. I prefer back panels with some serious airflow. How fatigued I feel along a hike has a lot to do with how hot I get. Being a “Hotlanta” Georgia hiker, Summer trips get Hot. My back is a huge heat-shedding surface, so I’m a big fan of the Osprey Antigravity system, as seen in the picture below, or similar mesh-backed suspension systems. Most of your big pack brands have an Antigravity-adjacent option on at least one of their packs these days, and I feel like most of them do the same job: get the solid surface of the pack off your back and circulate fresh air between you and your pack as you move.
On the other hand, most ultralight packs cut out the ventilation feature to save weight. I wasn’t a fan the HMG junction, with it’s back panel being nothing but waterproof pack wall directly against my back. It just did not fit me well to where I could get a good mid-back gap. The Six Moons Designs Minimalist was better, with foam straps and back padding lifting the pack away from the dip in the center of my back. This gives the Minimalist better airflow, but I still find the hot air getting trapped between the back panel and my back until I shift the pack around. I’ll add that I carried the 2018 Minimalist version in the picture below, and Six Moons Designs has since revamped the Minimalist into the Minimalist V2. The V2 seems to have less contact with the back when looking at images online, but I need to get my hands on one and hit the trail.
Every person is shaped differently. Your experience may differ, and I recommend trying the HMG yourself, but I wouldn’t carry the HMG Junction again myself since it seemed to stay wet up against my back as I hiked in the lukewarm temps of Fall. The Minimalist (2018 Version) was an absolutely pleasure in general, though I wouldn’t use it as my go-to summer pack. The Minimalist airflow is better than the Junction, but the 2018 Minimalist still isn’t quite for me. The Osprey Exos 48 does have the Antigravity style mesh in a lighter pack, but I’m drawing a personal line in the sand defining ultralight packs being less than 2.5lbs. Is the Exos 38 lighter than that unlike the Exos 48? Yes. Am I splitting hairs? Yes. Moving on!
Enter the Aerios 45.
This pack has all of your traditional ultralight features at 2lbs 6oz, but Arc’teryx comes out swinging with their Aeroform back panel, seen below. Is it a riff on the Antigravity type paneling? Sure. Is it totally novel in the land of backpacks? Nope. Do I care? Not a bit. The Aeroform back panel puts about a centimeter between your back and the pack wall with what appears to be a heat-formed dimpled mesh. These dimples are surprisingly strong, taking serious effort to press the panel up against the pack wall and springing right back. The moment I let go, the Aeroform panel pop back up with zero deformity.