The ZPacks Arc Air 50L ROBIC Backpack is an ultralight pack with a curved carbon fiber frame made with 100d and 210d Robic nylon. The backpack is a roll-top pack with a front mesh pocket, side water bottle pockets, and sleeping pad straps. It has an adjustable torso length so you can get a personalized fit and is available in five different hip belt sizes. While the hip belt does not have pockets, they can be purchased and attached to the pack, along with a wide range of other accessories including shoulder strap pockets, side mesh pockets, a Y-strap for carrying a bear canister, and ice axe loops. A 60L Robic version of the Arc Air is also available.
Specs at a Glance
- Weight: 21.2 oz / 600g
- Volume: 50L total: (37L main body, 2.5L each side pocket, 8L center pocket)
- Pockets: 3
- Fabrics: 100d and 210d Robic Nylon, Lycra Mesh
- Hydration compatible: No
- Bear canister compatibility: Vertical for a BV500, but you’re likely to feel it poking you in the back (I do).
- Max recommended load: 30-35 lbs
Backpack Frame and Suspension
The Arc Air 50L has a curved backpack frame like Zpack’s other packs, which is designed to let air flow between your back and the pack so your clothes dry faster when you perspire. It has a new frame that’s different from the one used on Zpacks other packs like the Arc Blast and the Arc Haul. The mesh back panel has been removed completely, the vertical frame stays are much thicker, and they’re sewn into the backpack improving durability and giving the pack a more polished look. The degree of curvature is also fixed, with a depth of 2.5″ (6cm), and not adjustable.
The new frame has some pros and cons.
The pros: The pack is simpler and less confusing to adjust which is a good thing, especially for new Zpacks customers. It’s also more durable because there are fewer moving parts and things to snag and tear on vegetation. I also think that the frame is stiffer, more responsive, and better at carrying heavier loads, like water carries, than the previous frame architecture. Part of that performance improvement may also be due to the fact that the pack bag sits closer to your hips because it has less of a curve.
The cons: The curvature depth isn’t really deep enough to provide a lot of ventilation when wearing multiple clothing layers. There’s some airflow (about an inch) behind your back if you’re just wearing a baselayer, but if you wear a hoodie or a jacket, they fill in and block the air gap. Then again, that’s a case where you probably want a bit less airflow in order to stay warmer.
If you prefer having a deeper and adjustable curvature with a mesh back panel to ensure that your clothing doesn’t block the air gap, you should probably buy the Arc Blast or an Arc Haul instead. Other than the frame, there’s not that much of a difference between the three packs other than the fabric they’re made with.
Incidentally, you can retrofit an Arc Blast or Arc Haul backpack to use the new Arc Air vertical frame stays. Contact Zpacks to purchase the replacement stays and to receive instructions.
Adjustable Torso Length
The Arc Air has an adjustable length frame (torso length) so you can dial in a good fit. The pack doesn’t arrive with any documentation that explains how to adjust it, but there’s a good video on the Zpacks website that explains what to do, although it’s for the Arc Blast series of packs.
It’s remarkably simple. Once you have the rest of the pack adjusted, you’ve packed the pack with a light load and put the pack on including the hipbelt, you push the shoulder pads down so they wrap around the top of your shoulders without any gaps showing. This positions the webbing that connects the top of the shoulder pads to the back of the pack at the proper length. That’s it. It’s a pretty ingenious design.
Shoulder Straps and Hip Belt
While Zpacks doesn’t make men’s and women’s specific backpacks, the shoulder straps on their packs are female-friendly with an S-shape that curves around women’s chests. The straps are also attached to the back of the pack with webbing instead of being sewn directly to the frame, which allows them to rotate and conform to the sides of your torso instead of lying flat on your breasts (and smashing them flat). This is beneficial to men and women, alike. The difference can take a while to get used to though and the space between the shoulder straps may feel a bit wide when you start using the pack.
The shoulder straps have load lifters that are attached to the frame and can be pulled forward to bring the pack closer to your back to counter any backward lean caused by a heavy or unbalanced load. There are also daisy chains sewn to the front of the shoulder straps so you can attach pockets to them easily or move the sternum strap position up and down.
While the hipbelt has a center buckle, you can adjust the fit on the top or bottom half of the belt using two webbing straps on each side. This is another female-friendly feature that lets you adapt to the shape of men’s or women’s hip shapes. The hipbelt is removable, but very tightly anchored on the frame, so you don’t lose any control or load transfer from the frame to the hips.
In fact, the load transfer to the hipbelt is downright awesome, it’s lightly padded so it won’t slip over your hip bones, and if you wanted to, you could easily adjust the pack so that 80% of the weight rides on your hips and 20% on the shoulders. Like the shoulder straps, there are attachment points on the outside of the hip belt where you can add pockets.
It’s worth mentioning that some people may experience lumbar discomfort using the hipbelt because it does not distribute the load across the entire base of the backpack, but focuses it on a narrower centralized area, between the vertical frame stays. I got used to this pretty quickly, but you may want to add a lumbar pad (sold by Zpacks) to add additional padding to this area if you experience discomfort.
Backpack Storage and Organization
The Arc Air 50 is a rolltop with a very standard ultralight pack design. It has a large main compartment, easy-to-reach side water bottle pockets, and a large front mesh pocket. The top of the main compartment closes with a velcro strip (some people hate this) and the buckles at the ends can be connected to one another or to buckle/webbing along the sides of the pack. There’s also a single webbing strap running from the back to the front of the pack, over the rolltop that can be used to lash gear to the top of the pack.
The curved frame doesn’t really interfere with packing bulky objects, which can be an issue with some ventilated backpacks that have deep cavities behind the back. But you’re going to want to pack items with hard edges closer to the front side of the main compartment (the mesh pocket side) rather than the rear, facing your back, so they don’t poke through the fabric and cause discomfort. This occurs because the spacing of the Arc Air’s vertical stays don’t provide the same degree of protection as you find on packs with more centralized frame stays.
The front mesh pocket is tightly fitted but has enough stretch that you can get a stove system into its, water reservoirs, snack bars, and rain layers without much difficultly. It has a fine weave and good transparency but could be ripped up by vegetation if you venture off-trail with it.
The water bottle pockets can hold 1L Nalgenes or 2 x 1L Smartwater Bottles and are slanted forward making them easy to reach while wearing the pack. They also have drain holes in the bottom to drain water and prevent it from collecting inside. The Arc Air does not have an internal hydration pocket or hook to connect a reservoir and there is no hydration port.
The Arc Air has sleeping pads straps, numerous gear loops, and daisy chains where you can attach extra gear to the outside of the pack. You don’t have to spend a lot of money to do this and a little cord, mini-biners, and cord locks can go a long way to customizing the pack for your need.
Alternatively, you can purchase add-ons from Zpacks from water bottle sleeves and shoulder pouches to hip belt pockets, to top side pockets, and a V-strap for carrying a bear canister. While these add-ons are very functional, they also add a lot of cost to the backpack that other manufacturers bundle in with the base price of their backpacks.
For example, let’s say you wanted to add 2 hip belt pockets ($29 each) to the Arc Air, which is a pretty standard feature on most ultralight backpacks from other companies. That’s $58 bucks. A V Top Strap is another $10. Ice axe loops are $10. Trekking pole holsters are another $10. It all adds up pretty quickly and you’re looking at close to $400 for a nylon backpack, which I think is pretty steep.
Arc Air Robic vs Arc Air DCF
The Arc Air 50L is available in Robic Nylon ($299) or DCF ($325) which is a pretty small price difference. How would you choose between them? I don’t think there’s a clear-cut answer to this question.
Personally, I prefer DCF over Robic because it doesn’t absorb water and it’s easier to repair with tape since I don’t sew. While the bottom of all of my DCF packs have all worn through in 3 years of hard use, DCF is much better for off-trail hiking, which I do a lot, because vegetation slides off it rather than puncturing it. I’m also ok with replacing my multiday backpack every few years so I don’t really care about wearing through the DCF at the bottom of the pack.
The high wear areas of the Robic Arc Air 50L are made with 210d Robic, which is pretty robust, but not as good as the 400d Robic used by other backpack manufacturers like ULA. If you don’t mind the fact that Robic absorbs rain despite its PU coating (this doesn’t add much weight, it’s just a hassle) I think it’s a good choice for trail-based hiking in terms of abrasion protection, particularly if you want to keep your pack for a lot longer than a few years. That abrasion occurs whenever you put your pack on the ground or when you rub up against rock walls.
Still, I do find it a bit confusing that the Arc Air 50L Robic is only $26 less than the Arc Air 50L DCF; I would have that the Robic Arc Air would be priced significantly less since it’s just nylon and probably requires a lot less labor to make than a DCF pack.
|Make / Model||Ventilated||Adjustable Torso||Interchangeable Hipbelts||Weight|
|Osprey Exos 48||Y||No||No||2 lbs 9 oz|
|Osprey Eja 48||Y||No||No||2 lbs 7 oz|
|Gregory Optic 48||Y||No||No||2 lbs 6 oz|
|Gregory Octal 45||Y||No||No||2 lbs 5 oz|
While all of these packs have ventilated frames with suspended mesh back panels, none of them have adjustable length torsos or interchangeable hip belts. They also weigh significantly more than a Zpacks Arc Air 50L Robic backpack which weighs 1 lb 5.
The Zpacks Arc Air 50L Robic Backpack is an ultralight roll-top backpack good for on-trail hiking with a ventilated frame, an easy-to-adjust torso length, and interchangeable hipbelt sizes to choose from, so you can dial in a near-custom fit. Weighing 21.2 oz, the curve of the Arc Air’s frame is fixed and not adjustable, making it much simpler to use, especially by customers new to the brand.
While the Arc Air 50L Robic is pricy, especially after you add on a few “accessories” like hipbelt pockets, there really isn’t anything out there that comes close to the value, in terms of fit, ventilation, and gear weight offered by the pack. My only reservation with the Zpacks Arc Air is that hard-edged objects can poke you through back panel if they’re packed behind your back and not toward the mesh side of the pack. But it’s easy to work around that limitation when packing your stuff in the backpack.
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