James Harris/CNN Underscored

Backpacking season has officially arrived, and whether you’re a seasoned thru-hiker or a beginner backpacker who’s just starting out, the features, cost and anti-chafing capabilities of a new pack can feel daunting to research, and testing out a variety of products on the trail is expensive and time-consuming. That’s why we’ve gone ahead and done some of the hard work for you by selecting two of the country’s top-selling backpacking packs and pitting them against each other in a head-to-head battle in the Rocky Mountain foothills to see which one came out on top.

We loaded up both the REI Co-op Flash 55 Pack and the Osprey Aura AG 65 with trekking apparel, a bear can, a tent, snack bars, a sleeping pad, a sleeping bag and 3 liters of water to assess how each one carried the same amount of weight, dispersed across their many organizational pockets. The result is a definitive comparison of the two packs, and below, we’ll highlight the pros and cons of each one so that you get a clear picture of which overnight hiking backpack is best for your trekking needs.

REI Co-op Flash 55 Pack vs. Osprey Aura AG 65 at a glance

Quick comparison

Fabric 100-denier recycled nylon ripstop and 210-denier recycled nylon
Weight 2 lb., 11 oz. (S)
Colors Yellow, Green
Pockets 9 plus main compartment
Price $199
Fabric Recycled 210-denier nylon, recycled 500-denier nylon, both with PFC-free DWR coating
Weight 4 lb., 7.5 oz. (XS/S)
Colors Gray, Purple, Red
Pockets 8 plus main compartment
Price $340

Fit and comfort

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Osprey Aura AG

Both the Osprey Aura AG and the REI Co-op Flash 55 Pack have excellent suspension that’s fit to comfortably carry several days’ worth of food and gear at a time, but both packs achieve that padded comfort in slightly different ways.

Like many of the brand’s packs, Osprey’s top-selling Aura AG features a 4-millimeter peripheral wire frame, which directly connects the upper load lifters and the center core of the backpack to the hip belt so that the load weight is evenly distributed and easily carried on your hips and legs rather than slumping into your shoulders and causing undue back pain. It also comes equipped with Osprey’s famous anti-gravity suspension, which is essentially a 3D mesh that contours the entire back and lumbar portion of the pack, helping to disperse and balance the load, even as you trek across the most rugged terrain. In practice, this helped me as I postholed for 2 miles through late-season snow to get to a still-frozen alpine lake in Rocky Mountain National Park with my partner. Though I was maneuvering over unstable ground, I was able to easily carry over 20 pounds in the pack as I watched my feet. And, perhaps more importantly, the pack offered tons of adjustment points to dial in that elusive perfect fit.

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REI Co-op Flash

The Flash 55 Pack, on the other hand, features a more traditional-style 3D contoured hip belt and a ventilated foam back panel, paired with a lightweight steel internal frame. Together, they make a formidable pair that could comfortably carry all of my overnight gear, including a 3-pound bear canister, and disperse it across my hips so that my legs could support the extra pounds. This rucksack also boasted adjustment points on the torso, hip belt, chest strap and shoulders to make sure the pack was well fitted to my body. Surprisingly, the pack itself is lighter than even the 50-liter version of the Aura AG, likely because it lacks some of Osprey’s bells and whistles (like an included rain fly). Looking for a lighter option? The 3-pound, 13-ounce Osprey AG LT 65 is more appropriate if you’re the ounce-counting type, and if you really want to go ham on a lightweight pack, grab an Outdoor Vitals CS40 Ultra, which weighs under 2 pounds.

Load carry and volume

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Osprey Aura AG

One thing I wish I’d known as a 5-foot, 3-inch-tall hiker when I first started backpacking is that smaller-sized packs often don’t hold the listed volume on that pack’s website. For example, the Osprey Aura AG 65 only holds a claimed volume of 62 liters if you order a size XS/S, and the capacity of REI’s Flash 55 is only 53 liters if you order a size women’s XS.

That being said, I’m a petite, stocky backpacker who routinely wears a size small, and I was able to fit all of my hiking clothes, a large BV500 bear canister, a tent, several snack bars, a sleeping pad, a sleeping bag, a spare water bottle, a headlamp and 3 liters of water in and around both packs with room to spare. They both carried the weight well, and we could easily stuff four energy bars into each roomy hip pocket on both packs, but it’s worth noting that REI lists its top recommended weight for the Flash 55 at 30 pounds, while Osprey claims that its Aura AG 65 can comfortably carry up to 40 pounds all day in the wilderness. If you’re a beginner who’s not yet ready to splurge on ultralight gear, you might find that your base weight with food and water edges closer to the 40-pound mark, which is important to consider. In the battle of maximum load carry, the Osprey comes out on top.

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REI Co-op Flash brain

We wished the REI Flash 55 came with the same bottom buckle straps as the Aura AG 65, because this is a handy area to store a sleeping pad or lightweight tent. We’d also love to see REI create a 65-liter version of this bestselling backpack, but for now, we’ll just have to settle for the more expensive and slightly heavier Traverse 60 Pack ($249).

Pockets and extra features

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REI Co-op Flash hipbelt pockets

Both of these backpacks offer loads of well-placed pockets for everything from trekking poles to protein bars to hydration sleeves. However, with nine smaller organizational pockets plus its main compartment (versus the Osprey’s eight plus its main pouch), REI Co-op’s Flash 55 Pack has a slight advantage in the pocket department.

That being said, it’s worth noting that both packs come with tons of fun extras that make stashing away your important outdoor gear a cinch. Both of these backpacks offer huge hip pockets that can carry several protein bars at a time, extra-deep, angled water bottle pockets, a hydration sleeve, ice tool loops, a secure key clip and a shoulder pouch. Both packs boast a spacious brain compartment that can be removed to save weight when needed. Where the extra cost and weight of the Osprey come into play are in additional features, like its large front zipper, dedicated sleeping bag area and included rain cover. Even though the Flash 55 is water-repellent (a feature I was grateful for when caught in a deluge outside of Lyons), users in soggy climates will want to nab a supplemental rain cover, like the Packmod Rainshield Pocket ($20), which is compatible with this design.

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Osprey Aura AG hip belt and pockets

Bottom line

While it’s true that the Osprey Aura AG 65 squeezed out narrow wins in all three of our categories, the much cheaper REI Flash 55 Pack held its own in a way that surprised our experienced backpacking tester, who’s spent more than a hundred nights in the wilderness. Both packs carried our sample load incredibly comfortably and provided a myriad of pockets to stash every little piece of gear we toted along on hikes in the Rocky Mountains.

Though it’s smaller than the Osprey, can carry less weight and lacks an included rain cover, we feel that the lightweight design, thoughtful pockets and easy adjustment points of the Flash 55 Pack will suit most users well, particularly if they’re newer to the sport and want budget backpacking gear. Trekkers who know they’ll be hauling closer to 40 pounds of stuff up and down mountain passes might want to splurge on the Osprey Aura AG 65, which costs $141 more, as its extra straps and anti-gravity mesh make for a comfy carry, even when you’re fully loaded up for a multiday adventure.