The Zpacks Arc Haul Ultra 60L Backpack is an ultralight, ventilated, and adjustable-length backpack made with Ultra, a new woven fabric made from Ultra High Molecular Weight Polyethylene (UHMWPE) fibers that is ultralight, waterproof, and more durable than Dyneema DCF. Weighing 19.6 oz, the Arc Haul Ultra 60L is set up like most ultralight-style backpacks with a roll-top closure, front mesh pocket, and side water bottle pockets. But what sets this pack apart from other ultralight backpacks, besides its incredible light weight, is a user-adjustable frame that lets you set the depth of the ventilation curvature and torso length based on your preferences and load characteristics.

Specs at a Glance

  • Weight: 19.6 oz
  • Gender: Unisex, but very female friendly (see below)
  • Pockets: 3 (hip belt pockets are available as an add-on purchase @ $32.95 each)
  • Hydration compatible: No
  • Ventilated: Yes
  • Bear canister compatibility: Yes – Vertical inside
  • Volume: 60L (47L main body, 2.5L each side pocket, 8L center pocket)
  • Fabric: Ultra 100 and 200, Lycra (front pocket), spacer mesh (shoulder strap/hip belt padding)
  • Max Recommended Load:  40 lbs (we rate it closer to 30 lbs)

Backpack Storage and Organization

The Zpacks Arc Haul Ultra 60L is shaped like most ultralight-style backpacks with a large main compartment, front mesh pocket, and side water bottle pockets. The main compartment closes with roll-top and has a narrow velcro-stiffener on top. A single strap loops over the roll-top to secure it. The interior is seam-taped, making the backpack highly water-resistant, although we’d still recommend lining it with a plastic bag or pack liner.

The Arc Haul Ultra 60L is an ultralight roll-top backpack
The Arc Haul Ultra 60L is an ultralight roll-top backpack.

The size and shape of the main compartment is significantly altered when the pack’s frame is arched to create a ventilation cavity. This is true of most ventilated backpacks. When the back of the pack behind your torso curves inward, it loses width and items can be harder to pack or unpack, since you have to reach around the resulting bulge. Packing your gear around a full-sized bear canister can also be challenging

The front mesh pocket is made with a Lycra mesh and has an elastic top. It can hold quite a lot of stuff at once and its easy to see whats inside so you know you haven’t misplaced anything. The mesh fabric is comparatively lightweight and less robust than the heavy duty mesh that other manufacturers are currently using to improve durability.

The side pockets are solid Ultra fabric for better durability
The side pockets are solid Ultra fabric for better durability.

The side water bottle pockets are made with heavier duty Ultra fabric with drain holes at the bottom and provide excellent durability. They’re large enough to hold two SmartWater bottles, but you can only get one 1L Nalgene into them. They also have non-adjustable elastic running through the top to keep bottles from falling out. While they’re reachable when the pack is worn, the elastic can makes it a little challenging to get a bottle back in if you’re carrying anything else in the pockets. That’s not a showstopper, just an observation about the structure and capacity limitations of the side pockets.

The Arc Haul Ultra 60L does not come with hip belt pockets and they’re an add-on purchase at $32.95/each. They are attached with an elastic band and hooks to the hip belt, which has daisy chains sewn on its exterior. The pockets are also available in Dyneema DCF or Robic Nylon for slightly less. The daisy chain can also be used to secure third party pockets to the hip belt.

The pack is not hydration compatible if that matters to you. There is no internal hydration pocket or hook to hang a reservoir. There are also no hydration ports in the pack body to run a hose.

The Zpacks Arc Haul Ultra 60L has a ventilated trampoline style frame.
The Zpacks Arc Haul Ultra 60L has a ventilated-mesh trampoline style frame.

Backpack Frame and Suspension

The Zpacks Arc Haul Ultra 60L has a ventilated, trampoline style frame that lets air flow behind your back so you stay cooler and perspiration dries faster. This makes backpacking much more pleasant in hot and humid conditions. Zpacks is unique amongst UL pack manufacturers in offering this type of frame. While other manufacturers, like Osprey, Gregory, and Deuter offer a similar capability, theirs is much more tightly integrated and encapsulated than the Arc Haul Ultra  frame which is completely visible, externalized, and adjustable by the end-user.

While this gives the Arc Haul Ultra a somewhat Frankenstein-like appearance with all kinds of straps and rods, it’s designed this way on purpose to keep the pack weight as low as possible. The downside is that the pack makes a little noise when hiking as the parts rub together. The closest comparable ultralight ventilated backpacks, the Osprey Exos 58 or Gregory Focal 58, weigh about twice as much as the Arc Haul Ultra, although the lastest (2022) Osprey Exos now has an adjustable length torso. Both these packs are also quieter to carry, because the frame is internal and all one piece.

The Arc Haul Ultra frame is quite simple. There are three horizontal crossbars, positioned along the top, middle, and base of the packbag. Two flexible carbon fiber rods are attached to the corners of the top and bottom bars and a mesh back panel is connected to them with webbing straps. When tensioned, the webbing straps cause the carbon fiber rods to bend and form an arc, with the mesh suspended over it. The middle crossbar keeps the pack bag from collapsing backward and filling the cavity created by the arc, while protecting your back from objects with hard edges like a bear canister .The backpack’s shoulder straps and load lifters are connected to the top crossbar, while the hip belt is attached to the bottom crossbar. It’s as simple as that.

The mesh back panel is connected to the corners with webbing straps. When you pull on them the top bar is brought closer to the bottom bar and a ventilation arc is formed.
The mesh back panel is connected to the corners with webbing straps. When you pull on them the top bar is brought closer to the bottom bar and a ventilation arc is formed.

When tensioning the arc, Zpacks recommends making it 2.5 inches deep. You can make it deeper or shallower based on your personal preferences. For example, you could eliminate the arc completely if you just wanted a very lightweight backpack without any ventilation or you need to scramble up a cliff face and want the pack’s center of gravity as close to your back as possible.

Despite the simplicity of the frame, dialing in a really good fit can require a fair amount of experimentation with different loads and arc depths. For example, whenever you create an arc, the distance between the shoulder straps and the hip belt (torso length) changes as well. Zpacks has a good pack fitting video that explains the basics (see sizing tab), but it can be a little time consuming to get a balanced and accurate fit that you can reproduce in the field if warranted.

Adjustable Torso-length

The Arc Haul Ultra frame was an adjustable length torso capability, which lets you raise or lower the height of the shoulder straps up to 4″. This can make a huge difference in the fit of the backpack and its load-to-hip transfer but is best done as a refinement after you’ve adjusted the arc to its desired depth.

Push down on the shoulder straps to shorten the torso length
Push down on the shoulder straps to shorten the torso length.

The torso adjustment mechanism is also quite simple. The shoulder straps are connected to two vertical interior webbing straps that are connected to the top crossbar and at points just above the middle crossbar. If you push the top of the shoulder strap down to lower it, you shorten the distance between the hip belt and the top of the strap, thereby shortening the pack’s torso length. If you raise the strap, you lengthen the torso length. It’s important that you keep two shoulder strap heights the same, so one shoulder doesn’t do more work than the other. The actual amount of torso length adjustment used is best done by feel while wearing a loaded backpack and after the arc depth has been set. See the Zpack’s pack fitting video on the Sizing tab for more details.

The Shoulder Pads are S-shaped which makes them comfortable for men and women
The Shoulder Pads are S-shaped which makes them comfortable for men and women.

Shoulder straps

The Zpacks uses S-shaped shoulder straps on their packs, which are better for men and women because they wrap around the pecs rather than smash them flat, like the J-shaped straps found on other unisex backpacks. The straps are not sewn directly to the crossbars or the pack bag but attached by a webbing strap that permits the top of the pad to rotate and conform to the shape of your shoulders for a more personalized fit. The shoulder straps are lightly padded and covered with wicking spacer mesh. The exteriors have daisy chains sewn to them that makes it possible to attach accessory pockets or reposition the sternum strap.

Hip belt

The Arc Haul Ultra hip belt is available in a variety of lengths so you can get a good fit. It’s also replaceable, which is nice if you gain or lose weight and want to change size. The hip belt also has exterior daisy chains suitable for attaching accessory pockets although none are included with the base backpack.

The top and the bottom of the hip belt can be tensioned separately providing a better fit for curvier female hips
The top and the bottom of the hip belt can be tensioned separately providing a better fit for curvier female hips.

The hip belt is female-friendly because it has upper and lower webbing straps that can be used to create a differential fit and accommodate curvy female hips or flattish male ones. The hip belt is lightly padded, which you’d expect on an ultralight backpack used to carry lighter loads. It provides a great hip wrap that doesn’t slip or buckle when you load the pack up with extra weight. It’s lightly padded relative to a heavier Osprey or Gregory backpacks, but perfectly comfortable with loads of 30 pound or less.

Load rating

While the Arc Haul Ultra 60L has a frame, its primary function is ventilation and doesn’t substantially increase the load-carrying capacity of the pack. I’ve carried multi-day loads with the Arc Haul Ultra 60L and find that the maximum comfortable load including gear, food, and water is about 30 pounds. I don’t think it’s all that comfortable with more, but you can certainly carry more for a long water carry if you have to. Zpacks rate’s the packs max recommended load much higher at 40 lbs, but that I wouldn’t say its very comfortable with that much weight.

Backpack Compression and External Attachment System

The Arc Haul Ultra 6oL is fairly light on compression capabilities and attachment capabilities but provides room for you to expand on them if you wish to customize them.

Cords can be used to attach a foam sleeping pad
Cords can be used to attach a foam sleeping pad

In addition to roll-top, which provides top-down compression, the Arc Haul Ultra has a static cord-based side compression system that’s tensioned with a line lock. There are also sleeping pad attachment cords at the base of the pack, which is a nice feature, not found on most UL backpacks. The same cord system can also be used or modified to carry an ice ax or even trekking poles, using the side compression cords to secure the shafts.

You can replace the side compression cord with webbing straps and gatekeeper loops
You can replace the side compression cord with webbing straps and gatekeeper loops.

If you want to replace the compression “cords” with a heavier duty webbing, that is easy using gatekeeper clips by sliding them into the webbing tabs sewn into the pack’s seams. For example, I prefer wider webbing straps when carrying a fishing rod or attaching snowshoes to the side of my backpack because they are easier to adjust and provide better holding power.

The rolltop clips closed on top and is compressed with a webbing strap.
The roll top clips closed on top and is compressed with a webbing strap.

Ultra Fabric

Ultra is being heralded as the new ultralight waterproof wonder fabric for making backpacks because it is more resistant to abrasion than Dyneema DCF in laboratory tests. I think the jury is still out on whether that’s true in the real world too. I’ve managed to wear out or destroy backpacks with every new ultralight backpack fabric that’s been introduced in the past 15 years; I’ll let you know how Arc Haul Ultra 60L is holding up to New Hampshire hiking and backpacking in about 2 years. Of course, by that time, it will probably have been replaced by something that’s supposedly even better. Whatever the case, don’t buy this backpack solely to have one made with Ultra. Buy it for its functional strengths and adjustable fit – which are both superb.

Comparable Backpacks


The Zpacks Arc Haul Ultra 60L is an ultralight ventilated and adjustable-length backpack designed for multi-day backpacking trips and thru-hiking.  Weighing just 19.6 oz, it’s significantly lighter weight than comparable backpacks even though it has a much more sophisticated and adjustable length frame system. While there is a higher initial learning curve to adjusting and fitting the Arc Haul Ultra than more conventional ventilated backpacks, once you’ve dialed in the fit, the backpack carries like a dream, comfortably transferring loads to the hip belt while keeping your back cool and dry. I really enjoy using this pack, especially in hot weather, where the suspended mesh frame keeps me much drier, cooler, and more comfortable.

If you’re trying to significantly reduce the weight of your backpacking gear and want a ventilated backpack, I’d recommend getting the Zpacks Arc Haul Ultra 60L. It is a sweet backpack, but definitely pricey.

Disclosure: Zpacks donated a backpack for this review.

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