Aer Ultra Sling (Pack Hacker x Aer Collab) Review

The Aer Ultra Sling is available starting March 2 at 10 AM EST. Limited quantities available.

Ten years ago, we tested the original Aer Travel Pack. Seventy products later, they consistently receive high marks via our rating system, and most of our team members carry at least one Aer item in their loadout at all times. So, when we got the opportunity to create our own product with Aer at the helm of design, we couldn’t refuse.

When discussing what to create, we kept coming back to the idea of a sling that blends extreme durability, seamless organization, and a sleek aesthetic. Aer was up to the challenge, so the collaboration began. After 17 months and countless emails, meetings, and mockups, we refined the Ultra Sling into something you can carry every day and on every trip. We tested zippers, tried different fabric samples, and refined every feature of the sling, down to the exact type of back mesh panel.

The result? A 2-liter sling that pushes the boundaries of functionality, style, and performance in travel gear. Let’s get into the details.

External Components

The Ultra Sling’s look changed significantly over time as we refined each iteration. We started with squared edges because they’re easier to pack, though we thought they looked a little too blocky. After a bit of back-and-forth, we settled on a rectangular design with rounded corners, which creates a softer profile that looks better on the body. You sacrifice a little capacity in the corners compared to a square bag, but we think it improves the bag’s overall aesthetic.

Next was the challenge of figuring out the best material for the job. The original nylon fabric worked—until we got caught in a week’s worth of rain in Lisbon. That completely soaked the bag and the gear inside. This inspired our change to the rugged Challenge Sailcloth Ultra200X fabric; it adds a ton of weather-resistance, especially paired with these reverse-coil YKK zippers. Their design makes it even harder for water to seep through, providing an extra layer of protection in wet conditions. ULTRA fabric is about more than just staying dry, though. It naturally resists fading from UV rays and has an excellent strength-to-weight ratio, preventing tears despite its light weight.

Even the Hypalon zipper pulls are built to last, providing plenty of grip so you can easily open each compartment. The pop of color at the ends is subtle, adding a little Pack Hacker flair without straying from the classic Aer style. Apart from the occasional accent, there’s no loud branding on the bag. Instead, we kept it simple with debossed “Aer” and “Pack Hacker” on the pulls and thoughtfully placed “Aer” Hypalon tabs on the straps’ sides.

Subtlety is the name of the game with this sling. Hidden at the bottom is a pair of lash straps that sit flush against the base until you want to use them. We like to attach a MODL Infinity Tool 2.0 to each side, giving us a spot to hang an umbrella, so we’re not carrying it around all day or upgrading the size of our everyday carry bag just for rain gear. You can also use it to hold a rain jacket, travel tripod, or pretty much anything else oversized. If that’s not enough dangle space, there are two more loops where the shoulder straps attach, which you can use to hang additional items.

However, nothing compares to the feature we love the most: the shoulder strap. The Duraflex buckles swivel, allowing the bag to pivot and fall naturally against your body, whether you wear it tightly or loosely. This was a labor of love between the Aer and Pack Hacker teams. The original version had the strap sewn right into the sides, and, as with other slings of a similar design, we found that the strap wrinkled and buckled awkwardly at the edge of the bag, affecting the overall aesthetic. Aer Co-founder and Head of Design Allen Choi suggested switching to a pivoting buckle to fix the anchor issue, and the rest is history.

As a bonus, the straps are also removable. Press the center button at the attachment points to detach the hardware, and you can use the sling as a standalone pouch instead. It’s a great feature for one bag travelers who don’t always want to carry a sling but like to have the option when they land.

The nylon strap has a seatbelt-like feel that’s comfortable against your body but thin enough to be packable. We often find thicker straps on small slings to be overkill, so this one hits the sweet spot between packability and carry comfort.

Something we didn’t initially think was needed was a mesh back panel. It may seem like overkill for a bag of this size, but the benefit of working with bag designers is that they have a solution for everything! The first iteration of this sling had a slick back panel made of the same nylon material as the rest of the bag. While this looked nice, we found that the bag kept slipping out of place when wearing slick clothing, such as a rain shell or puffer jacket. After adding the mesh, the bag stopped sliding out of place, allowing us to spend more time exploring and less time adjusting the fit.

Speaking of which, let’s chat about how this sling feels on your body.

Fit Notes

With a 2-liter capacity, it’s no surprise that this bag looks good on any body frame. Of course, those with petite builds will find it covers more of their torso than those with larger builds, but the swivel buckle helps refine the fit. Adjust the sling to where it feels most comfortable on your body, and the buckle will work with gravity so the bag falls naturally. The strap adjusts via a closed loop system, so no matter how tightly or loosely you wear it, you won’t have to worry about keeping dangling strap material in check with keepers.

We prefer to wear the Ultra Sling around the mid-chest area, though it works just as well as a crossbody if you extend the strap to keep it closer to your hip. Tighten it even more, and it’ll stay as close to your body as possible. No matter how you wear it (front, back, ambidextrous—you name it), there’s no buckle on the strap to dig into your back when you pair the sling with a travel backpack. Simply slip the Ultra Sling over your head, adjust it to your preferred fit, and hit the road.

Inside The Sling

Everyone on the team uses this bag a little differently. That’s what makes a good bag great. While this sling looks simple, it’s packed with features that you can make your own.

Each pocket is lined with a light grey, bluesign® approved ripstop nylon material that adds visibility when you’re looking for your gear inside. That’s less of a concern in the front pocket, which has a unique, built-in organization system to keep your gear exactly where you left it.

The quick-access front pocket has sections separated by an elastic panel, creating an accordion shape that keeps gear organized. Sometimes we love a good dump pocket, but the organization here makes finding small items effortless and keeps keys from scratching other gear. The first version of this pocket was just an open space. That was fine for dumping things in, but it gave the bag a lumpy shape, and we don’t like having to dig around to find things inside. The more we talked with Aer, the more ideas we had for organizing this pocket. On the next iteration, we added two liner pockets to the open space. This worked well at first, but we found it too fussy to put items inside. Instead, the final iteration features a dump pocket split into three sections, with a wider opening so you can easily store small items wherever they fit best.

On the left, we keep tall, round items like inhalers, lip balm, and a multicable. The center is perfectly sized for AirPods and earplugs for on-the-go noise management. On the right is a key leash with a carabiner clip, keeping your keys separate at all times so they won’t scratch the other gear in the pocket. We’re incredibly pleased with this design, as it adds organization in a pocket that often feels like an afterthought.

Flat items are best suited to the back zippered pocket. This is where we keep a passport wallet for international trips, a face mask to reduce the effects of air pollution, and a phone (unless you want to keep it in the main compartment—more on that later). The mesh back panel adds a little extra cushion to buffer the feel of any bulky items, and the fabric welt hides the zipper track and pull, making this almost a security pocket. In fact, we’ve had this sling checked before entering a club and a movie theater, and even searched by Thai police, and we’ve yet to have anyone even notice this back pocket. Sneaky movie snacks, here we come!

Everything else goes into the main compartment. However, it doesn’t lack organization. The rear slip pocket is the perfect size for a Kindle, making it great for readers who like to keep a book on hand at all times. It’s also that alternative spot for your phone we mentioned earlier. Or maybe you’re trying to journal your trips and would like to keep a notebook here. The possibilities are endless! No matter what’s inside, though, the slight padding protects your screens without cutting into the main compartment space. After all, that’s where you’ll be storing the bulk of your items.

While it’s open to pack as you please, we have enough space for a wallet, glasses inside a case, a battery bank, a mobile tripod, and gum. That may not sound like much, but it all adds up when you’re packing inside a small sling. And, since there’s a little space to spare, you can add things like a light pair of gloves, a hat, or some toiletries to freshen up after a long flight.

So, what about all the other stuff you pick up along the way? Receipts, transit cards, and a ton of spare change in countries where cash is still king? Enter: the pocket we’re affectionately calling “The Junk Drawer.” This zippered area is separated from the main compartment by a mesh material that lets you pack it out with oddly shaped gear without it bulging too much into the rest of the sling. We stick pretty much anything that would otherwise muddy up the main compartment here, accessing it as needed while exploring new cities and cleaning it out at the end of the day or next time we see a trash can. Without a pocket like this, any gum wrappers are at risk of falling out of the sling every time you pull something out, which isn’t a good look anywhere in the world. If you’re not a packrat, you can also use this zippered space for dongles, cables, or anything else small that doesn’t need to be in the sling’s front divider pocket.

In this area is also a hidden smart tracker pocket. The opening is tucked slightly under the zipper, so it’s hard for any ne’er-do-well to find, but not so difficult that you can’t easily add your tracker. Tiny details like this, and the Hypalon brand label above the pocket that doubles as a pen slot, are exactly the kinds of thoughtful touches that make us excited to work with a company like Aer. The team pays close attention to customer feedback and looks for ways to improve products with features that frequent travelers actually use.

While we’re a bit biased, we love how this sling turned out. Between our experience and Aer’s product development, we’ve created a functional sling that can go anywhere and looks good doing it. We’re so grateful to the amazing team at Aer for helping us make a bag that works equally well for everyday carry and trips across the world.