The Zpacks Arc Air is an ultralight external frame backpack with roll-top closure, full sized shoulder pads, and a full-sized hip belt. I have the 50L DCF version. I also included several add-on features: two hip belt pouches, a shoulder pouch, ice axe loops, a Y-strap top closure for bear canisters, and a side top pocket. Other add-ons are also available.
This review is based on use through 10 hiking days across five overnight trips in Georgia and Tennessee with a range of temperatures from around 80F to 20F carrying a base weight of 8.7-13.0lb and total weight of 14.0-19.5lb. I have not had rain during the day on any of these trips. Humidity has ranged from low to high. Mileage has varied from 3 to about 17 miles per day. Terrain has been mostly low mountains in the southeast of the US, ranging from relatively flat and lightly wooded areas, to steep and somewhat rocky trail, to boulder fields requiring significant rock hopping for several miles.
Link to Youtube version of this review: https://www.youtube.com/watch?v=EJvBU2bWoXQ
Specs
The pack comes assembled with the add-ons. With the exception of the y-top strap I haven't taken apart everything to weigh separately.
Size: 50 L, medium torso, small hip belt
Material: DCF (Dyneema composite fabric)
Weight: 24.15 oz total (actual) [this is about 0.65oz over the total claimed weight]
base pack: 20.1 oz, 571 g (claimed)
y-strap: 0.5oz, 16g (claimed); 0.6 oz, 16g (actual),
hip belt pouch: 0.8oz, 22g each (claimed)
shoulder pouch: 0.6oz, 17g (claimed)
side top pocket: 0.5oz, 14g (claimed)
ice axe loops (one pair each side): 0.1oz, 3g (claimed)
Cost: $452 total
[purchased by me at full price, there is no sponsorship here of any kind]
$325 for base pack
hip belt pouches $50 for the pair
shoulder strap pouch $32
Y-strap $10
Ice axe loops $10
top side pocket $25
Features, Comfort, and Usability
Frame - the Arc Air has a curved carbon fiber external frame designed to "arc" the pack away from your back allowing airflow to keep you cool and dry. It consists of two curved stays with a square-ish cross-section (about 3/16-inch) running vertically up the sides of the pack, and three 5/16 inch wide, thin flat horizontal stays (top, bottom, and middle) to add structure and rigidity. If packed relatively loosely the arcing feature for airflow generally seems to work as designed, and my back has been much less sweaty than with an internal frame or frameless pack. However, overstuffing by compressing the sleeping bag can cause some bulging of the pack fabric between the stays. This reduces the gap in the lower lumbar region and can eliminate the gap for perhaps a 6x8 inch area of additional contact with your back. Packing thoughtfully reduces or eliminates this issue. The reason I chose an external frame pack was for load transfer to my hips due to a recent back injury that required surgery on my L5-S1 disc. This frame transfers the load beautifully when adjusted properly. I have also found the load to be very stable, even on rough terrain equivalent to moderate off-trail experience.
Shoulder straps - the 2.75 inch wide, nearly 1/2 inch thick (3/8 inch foam plus the sleeve), 3D spacer mesh with tricot lined shoulder straps on this pack have adjustments on the frame to match your height. I did not need to change the position, though it is not hard to do. The 3D spacer mesh lining on the straps has been reasonably comfortable for me. However, under high humidity this fabric can feel a bit abrasive or scratchy if you like to have some weight on your shoulders and you are sweating when the humidity is high. This is partly due to the 1/2 inch webbing running along the center of the straps carrying most of the load and creating pressure near the collarbone if you have the straps too tight. Proper adjustment avoids this issue, allowing the width of the strap to better distribute the pressure. The shoulder straps come with easy to use and effective load lifters, and a daisy chain to attach items such as a shoulder pouch, umbrella clip, etc. The shoulder pouch is relatively easy to move up and down on the chain. A stretch-cord umbrella clip (from Gossamer Gear) seems to work well, but I have only tested this at home, not on the trail.
Hip belt - The hip belt is made of the same material as the shoulder straps except that it uses two separate 3/4 inch wide strips of webbing that join in a Y configuration from each side to meet at a single buckle. The Y-joint allows for four adjustment points, two on each side of the belt. I have found the hip belt can be problematic for comfort when worn tightly to increase stability over rough terrain. On the Fiery Gizzard trail, which has several miles of boulder strewn river gorge, I experienced some pinching and chaffing that resulted in a very thin scab forming around much of my waist. This was partly my fault due to allowing the belt for my pants (1 inch thin webbing) to be compressed or pinched under the belt on the pack. However, I have hiked with other packs and the same pants/belt under similar conditions without this problem. Adjusting this position on a later trip and slightly loosening the belt reduced this problem significantly. It prevented the chaffing but did not completely eliminate discomfort unless I was mindful to keep my pants, belt and shirt positioned appropriately under the belt.
Main compartment - The main compartment has a single-access opening from the top with a 1/2 inch velcro closure stretching across its length. At each end of the opening is a 3/4 inch clip. This combination is designed to work just like a dry bag. In addition, a convenient grosgrain pull tab is located in the center of the opening to pull apart the velcro and open the bag (this is very easy to do). The clips for the roll-top closure can either be connected to the side compression straps or to each other when closing the bag. I find this dry-bag closure system to be very versatile and convenient to use. However, I find the velcro strip to be problematic for loading my gear. It constantly pulls at the fabric of my clothing as I reach into and out of the bag. This can be quite annoying for certain materials and can cause some abrasion. I also worry about potential abrasion to my sleeping bag, puffy, or other gear I load into the pack. I would prefer a simple button closure in the center rather than the velcro.
Side Pockets - The two side pockets are roomy enough for two Smartwater-sized bottles each, though that is a tight fit. I use one on each side and find there is plenty of space for my umbrella, tent poles, or other longer items I want to keep out of the main compartment. These side pockets are designed with an angled elastic and accessible from the top only. I am able to remove and replace the water bottles without having to stop and remove my pack, as intended in this design. However, this does take practice and I am still finding it harder than I would like. This is somewhat compounded by the elastic cuff. If you wear your pack high on the waist, as many recommend nowadays, this makes removing and replacing the bottles even more difficult.
Center pocket - the lycra stretch center pocket is approximately 10x15 inches unstretched. This is roomy enough to hold my 20x48x1/8 inch evazote foam pad along with a variety of poky gear like tent stakes and my long-handled spork, or other items I like to keep on the outside of my pack such as my toilet kit, a 4x8 foot polycro groundsheet, sun gloves, and more. If you need it to, it can hold a lot more. I added both of my shoes (mens size 12 Altra Lone Peak 5s) for a recent trip with a river crossing.
Hip-belt pouches - I really like this add-on. For me, it brings a whole new dimension to the usability of the pack. I keep most of my small items in these pouches, leaving the need to open the main compartment mainly just when I get to camp or when I need a major change of clothing as weather conditions change. I bought a pouch for each side of the hip-belt and and am very glad I did. They are easy to attach, voluminous (~1L capacity each), simple, and highly water resistant due to their taped seams and waterproof zipper. I use one for snacks and sometimes my phone, and the other for a variety of small items such as my first aid and repair kits, knife, emergency fire starter, toothbrush and related items, soap, suncscreen, bugspray, etc. I do have two have minor complaints about the hip-belt pouches. First, the simple open space is a bit too roomy for my small items. I can put so many items in there that things become hard to find. Some additional organization using tiny ziplocs may be needed. Second, the Zpacks logo sewn onto the center-top of the pouch (it is seam taped on the inside) has corners that snag the sleeve of my shirt as I hike. This happens on just one side and I believe is due to the way it happens to naturally sit with the logo position puffed out towards my sleeve. I can make it go away by pressing the pouch center at the top in towards the belt, but I have to remember to do so after each use or each time I take off the pack and set it down. I recently decided to carefully remove the logo to prevent this problem (this is kind of a pain to do when trying the maintain the seam taping integrity on the inside).
Shoulder strap pouch - this pouch has two compartments - a DCF inner sleeve with a cinch closure sized for a Smartwater bottle, and a smaller mesh outer with elastic closure. For me, there are two important uses for this pouch. First, I keep my Inreach Mini inside the main sleeve, with the antenna sticking out the top. It is easy to access this way. Second, the mesh outer snugly fits my iphone. I find I use the phone a lot more when I keep it in this pouch right where I can see it and grab it nearly instantaneously. I also keep the sun cape for my OR hat, my bug headnet, and my headlamp in the main sleeve. I keep those items there mainly so the Mini can sit on top of them to stick out slightly.
Top side pouch - this pouch attaches to the side of the pack near the bottom of the roll-top. It has a 2.5L capacity and is about 6x3x8 inches. I use it for my cook system. With care, it barely fits my Evernew 1.3L pot inside its pot cozy. In the pot I keep my fuel, stove, lighter, and cleaning cloth. My 0.9L Evernew fits this pouch much more easily. I haven't used this pouch for anything else, though it can help secure a tall item such, as an umbrella, so that the item won't flop around. My intent in purchasing this add-on was to be able to hike and cook all day without opening the main compartment. However, I am not sure this item is worth it, especially when carrying my larger pot in its pot cozy.
Shock cord, ice-axe loops and side straps - the only item here I consistently use is the side compression straps. I like to use these with the roll-top closure clips to help minimize the pack profile. I find they don't provide much for compression from front to back given their geometry, but they do help vertically by pulling the roll-top ends down and at the same time provide additional weatherproofing as they do so becuase they secure the rolled opening. They can also be useful to keep an umbrella or other tall item secured. Regarding the shock cords below the center pocket, I haven't found much use for them. Many people use these for Z-lite type foam pads or rain gear. I just haven't needed them. I also haven't hiked with an ice-axe yet, but I did use the ice-axe loops to help secure some tent poles when hiking with my family.
Construction Quality and Expected Durability
Main compartment and side pocket stitching, seam sealing, and DCF durability - I have found the quality of the stitching on this pack to be excellent. Some have complained about Zpacks stitching, so I checked this pack over fairly thoroughly. The stitching is solid, straight, and even (see image below). The seams on this pack are taped, making it essentially a waterproof pack. I still use a pack liner just in case. However, I would be confident that my gear would remain dry on a trip with light to moderate rain. The material used for this pack is 3.1oz/sqyd Dyneema. This fabric has a stated puncture strength of 7.3 lb. This seems like you wouldn't even be able to set it down on the ground without puncturing objects penetrating it. However, in practice this fabric appears significantly more resistant to both puncture and abrasion than my prior spinnaker cloth pack. I am pretty careful with my gear, so I find the durability quite acceptable. In fact, were there an option for a slightly thinner Dyneema I might opt for it.
Hip belt pouches - these pouches will undoubtedly last a very long time, as they are also made of 3.1oz/sqyd Dyneema. The seems are sealed and the waterproof zipper appears solid. I do find that it can be difficult to open the zipper with one hand unless you have carefully placed the zipper pulls in the correct location. Finally, the clips used to attach the pouches to the belt seem flimsy when you look at them, but when handling them they are tougher than you might expect.
Belt and shoulder straps - I can't yet determine how the foam padding on these items will stand the test of time as sweat and dirt take their toll. The construction is high quality, with the strap attachments cross-stitched, double stitched, and only two thread ends visible anywhere (see image above).
Center pocket - the lycra stretch fabric on the front pocket has stood up well on other pack models over time. Weak points might include the overlapped fabric around the elastic band along the top, and the stitching that secures the pocket to the pack body. The elastic band stitching appears quite professional, and a double row of stitching along the border of the pocket secures it to the pack. These areas show no wear after four trips. However, I do have some concerns about the top corner stitching where the pocket opening begins at each edge (see image below). These corners are not cross-stitched. Rather, they use an angled V-stitch on the folded lycra. This results in significant tension on the stitching at that point. Further, one side has a loose thread visible, as show in the image. I will need to monitor this over time to see how it holds up. This may be the least confidence building feature in overall design on the entire pack.
Overall Impression
Am I happy with my purchase? Yes. This pack is a durable, easy to use, feature-rich, ultralight pack with a frame and hip belt. For someone with back issues needing a frame, this pack performs admirably. The two biggest negatives for me are the velcro on the main compartment entry, and that the hip belt requires some care to avoid chaffing. Is it the perfect pack? No. However, for my needs it is completely functional with the add-ons. Overall, I am looking forward to many more miles with this pack.