Gear Review: Sierra Designs Flex Capacitor 60-80L or: Why I Ditched My Osprey Atmos AG
Introduction
I have never been able to get into ultralight backpacks as I value the comfort of a pack that rides well over the reduction in weight offered by the fanciest of ultralight packs. In fact, some oof the ultralight packs I’ve tried have taken me back to my military days, lugging around an annoying seabag. The opposite of the seabag is the Osprey Atmos AG (“anti-grav”) with full mesh suspension, which I’ve loved beyond measure since 2016. I’ve used both the original anti-grav version and a newer version I acquired after 2020. Note: I also have smaller packs that I use for different missions, which are only rarely featured in trip reports.
Below: My new and old Osprey Atmos AGs.
But that recently changed. 65L hadn’t quite been cutting it for taking gear for me, my daughter, and sometimes others, so I was looking to upgrade. While perusing around at the expensive, heavy options, I came across the Sierra Designs Flex Capacitor 60-80L, and reviews were sparse. I found basically one mention of it on a forum, where a man commented that he’d used it well in the Winds. Well shucks, I was a Winds guy, too. I looked around and snagged it in a dark grey (I like colors that don’t stand out) for $189.95 shipped. Wow! Also, I purchased it at CampSaver.
More importantly, the pack used 100D Nylon Honeycomb/420D Nylon Oxford and weighs 3lbs 2oz. My Osprey weighed 4lbs 13oz, so the weight savings were decent enough (extra gummy worms, yum!). I was a bit worried about a few things, though:
- The Flex Capacitor had only one zipper compartment in back, so there are a lot less options for access.
- It also had a Y-shaped metal stay that provides all the support. That puppy could break.
- It didn’t have 3D mesh, instead being of an older-school design with just a couple of squishy, mesh pads near the shoulders providing most of the breathability, which could mean horrible, sweaty spots and rubbing of salt, and thus chafing.
Of course it did have some nice features, and wasn’t totally barebones. For example:
- Ability to expand from 60-80L (duh)
- 2, very large, mesh side pockets
- 2 stretchy pockets on the shoulder straps
- 2 very large zipped pockets on the waist
- An internal, hanging pocket against the back
Real World Use in the Wind River Range and Gros Ventre
If I put the bottom line up front, after ONE use of the Sierra Designs Flex Capacitor 60-80, I stopped using my Osprey completely, and not just to test it out. I’ve backpacked with it in the Winds and Gros Ventre for about 200 miles now and gone off-trail all over, especially on the eastern side of the range, and it basically still looks brand new.
Below: A variety of terrain over which the pack was taken.
Here are some things that I noticed when using it, and while some of them might seem negative, that shouldn’t be the takeaway of my opinion, as I LOVE this backpack:
- Heat and sweat were no issues. I hiked on the hottest day I’ve ever hiked in the Winds and didn’t even notice it.
- The hip belt kind of “floats” around, which means that I had better balance with it while ambling.
- It did have a tendency to kind of compact itself between my iliac crest and ribcage given the size of the hipbelt, but a simple loosening of two straps fixed that any time I knew it could be a problem, and it took me only 10 seconds to figure it out. It was so simple that I found myself not bothered at all by it, and the return to standard adjustment takes literally less than a second. “Zip zip, zip zip.”
- Like any pouch, the ones on the shoulder straps can lose items, so make sure you have some sort of retention device there.
- There is no whistle built in, if that affects your decision.
- The waistbelt pockets are MASSIVE. My friend Sarah Lefor says that they are even more impressive than her funbags. (She apparently owns bags filled with fun things, and knowing her, that means PICKLES. You will find a picture of the harridan below.)
- I was able to look up with the pack full stuffed.
- The pack gets very wide when fully expanded, but it never pulled on my back or threw me off balance.
- I never wanted more pockets, which shocked me.
- Getting into the main compartment was actually very easy as the back wasn’t as rigid as I was used to.
- Expanding and contracting the volume took about 10 seconds each way. Awesome.
- I don’t use water bladders, but it would work well if you wanted to.
- I was able to secure my solar charger to the back without any issue. I’d worried that a lack of anchor points would be a problem.
Below: Some normal pictures of the pack, with the bottom photos taken during a 6-day outing.
I ended up being shocked by home much more I preferred the Flex Capacitor over the Osprey Atmos AG. Strangely, though, the Osprey’s rainfly actually worked better than the Flex Capacitor’s, which I annoyingly had to order separately. The rainfly that Sierra Designs makes is kind of a loose-fitting piece of equipment that doesn’t secure as well as the Atmos’ one, which seems bizarre, as obviously the Atmos rainfly shouldn’t work better on a bigger pack with a different shape.
Below: You can see part of the wishbone main stay, which looks very akin to my (broken, thanks to my mom) Big Agnes Copper Spur poles, and gives me pause when stuffing the pack full. I try to avoid putting hardened materials against the poles. Lastly, the “floating” hip belt, which I love. You can see how huge the side pockets are. You could store a small Latina in them.
Durability
I’ve only used it for one season, but I have NOT been kind of the pack. It looks basically still new, but I do have worries about the Y-stay. It that thing breaks, you’re going to have to splint it and hope that it works out, but it could ruin a trip. I would be careful with how you stuff things against it. I’ll update the durability rating in 2025…if I remember. (And I’ll probably only remember if it breaks.)
Summary
The Sierra Designs Flex Capacitor 60-80L has replaced my Osprey Atmos AG 65 as my preferred pack. It shaves off a significant amount of weight while retaining comfort under heavy loads, finding an excellent position between ultra-light and ultra-rigged packs, and the price simply can’t be beaten. Although it has fewer bells and whistles, I haven’t minded that even a tiny bit.
Final Rating
The Sierra Designs Flex Capacitor 60-80L is my favorite backpack ever.
