Arc Blast 55L Backpack

135 reviews
$375.00 Weight 19.9 oz / 565.0 g

Lead Time Ships in 1-3 days

Great pack and exceptional quality. This pack is a must have for anyone serious about backpacking and moving around light. Quality design and craftsmanship. Thank you Zpacks. Fine job.

– Vincent C., ★★★★★

Designed to hike along mountain trails, scale steep ascents, and weather those Appalachian rain storms, the ultralight Arc Blast is perfectly suited for the demands of long distance hiking.

Comfortably transfer your pack’s weight to your hips with our patented ‘Arc Frame’ system.  The frame also creates a gap between your back and the pack allowing for air flow that helps keeps you cool.

Featuring adjustable shoulder straps, an interchangeable belt, and a variety of optional modular add-ons, the award-winning Arc Blast will allow you to tackle those long days on the trail with a durable ultralight backpack designed to fit you.


  • Constructed from 3.1 oz/sqyd Dyneema® Composite Fabric Hybrid. 

  • Roll top closure (like our dry bags) keeps water out, and lets you roll down the top as your gear load shrinks. All seams and attachment points are taped, making the pack highly water resistant. We still suggest using dry bags for your important items like your sleeping bag.

  • Comfy 3/8" thick by 2.75" wide padded contoured shoulder straps and padded belt. Both the straps and the belt have a daisy chain for clipping on items, and an adjustable position sternum strap is also included. The belt and shoulder straps have 3D mesh on the underside. This gives them a little bit more cushion, and the belt also has more texture for better grip.

  • Side pockets are sized to fit 1 or 1.5 liter bottles. They are positioned low on the pack and slanted forward for easy access without removing the pack. The pockets have drainage holes at the bottom, and elastic that keeps them tight at the top.
  • Large stretchy mesh center pocket is great for quick access items. Mesh also lets you dry wet clothing and gives you a clear view of your gear.

  • Side compression straps are made from non-stretchy Dyneema® cord for squishing down the pack volume. They also allow you to stand tall items like trekking poles in the side pockets.

  • A top strap, and base straps allow you to lash on extra items to the top or base of the pack. The straps come off if you don't need them.

  • A centrally located Hydration Port is included to string out a drinking tube over either the left or right shoulder. It is just above/between the shoulder straps and it has a triangular cover to keep out water. A water bladder can either be hung from an internal hang loop or laid horizontally on top of your gear.

  • The 55L pack size has enough space for 5-6 days of food and ultralight gear. The pack can be compressed down with the roll top and side compression straps for short trips or use the top strap and base straps to lash extra stuff to the outside for long carries.

  • All standard Bear Canisters, including the Bearikade Expedition and the BearVault 500 will fit in the upper half of this pack standing on end. There is enough extra girth to either wrap a foam pad around the canister (if you use one) or stand a medium stuff sack vertically beside the bear canister.

  • The short and medium size frames will fit into an airplane overhead bin with the top rolled down to the frame. The tall size frame may not fit unless you pop the vertical frame bars out of the pack.

  • Our Flexed Arc Frame is is covered by US Patent No. 9,060,590

  • Our torso height adjustment mechanism is is covered by US Patent No. 9,848,687

  • All Zpacks gear has a two year limited warranty against defects in materials or workmanship. Please see our return / warranty policy.

  • Made in the USA.
  • Our ultralight Flexed Arc frame keeps the pack stiff so that most weight is carried on the hips instead of the shoulders. The frame pieces and mesh back panel can be easily removed or replaced.

  • The frame is curved to allow air flow and keep your back cushioned from the pack's contents. You can adjust the curve by tensioning the mesh back panel. The recommended arch is about 2.5" (6 cm).

  • The belt is attached directly to the bottom of the pack frame for the best load transfer.

  • The belt is removable and interchangeable. If you lose weight or need to share the pack between people, the belt can be swapped out. Watch the belt removal video.

  • The shoulder straps and load lifter straps are attached directly to the frame. Load lifters straps come standard on this pack.

  • The shoulder straps can move up or down to adjust the torso height to a perfect fit using our patented torso adjustment mechanism. It works like a conveyor belt. This is great for sharing the pack between people, for growing teenagers, or for resale.

  • The belt provides a full wrap around your back. No need for additional lumbar support.

  • The belt is done with "V-Style" webbing so that the top and bottom circumference can be adjusted independently. This helps wrap your hips much more securely and prevents the belt from sliding down.

  • Collectively, these features provide the additional load transfer necessary for loads up to around 35 lbs (16 kg).


Body dimensions: 7" x 12.5" x 30"  (18 cm x 31.8 cm x 76 cm)

Volume: 55L (42L main body, 2.5L each side pocket, 8L center pocket)

Frame Height: Short 19" (48.3 cm), Medium 21.5" (54.6 cm), Tall 24" (61 cm)

Made with Bio-Based Dyneema® Fiber

Reduce your carbon footprint with DSM’s bio-based Dyneema® fiber technology. Sourced from renewable, bio-based feedstock, it is the first ever bio-based ultra-high molecular weight polyethylene (HMPE) fiber. Commit to sustainability and help reduce our reliance on fossil fuel resources and rely on the trusted performance of the world’s strongest fiber™. Click here to learn more about our sustainability initiatives.

Made in the USA.

3.1 oz/sqyd Dyneema® Composite Fabric (Hybrid)

Dyneema® Composite Fabric is composed of high strength Dyneema® fiber laminated inside a polyester membrane. It is inherently waterproof and does not require any coatings or DWR treatment. Dyneema® Composite Fabric has very high tensile strength for its weight and does not stretch.

This hybrid version is made from 1.6 oz/sqyd Dyneema® Composite Fabric on the inside, with an extra layer of protective 50 denier polyester on the outside. The outer layer gives it more strength and abrasion resistance, prevents fraying, and gives it a nice solid color. 

Tensile Strength:
 245 lb/in (2150 N/5cm)

Puncture Strength: 
7.3 lb (32 N)

Water Resistance:
 >20,000 mmH₂O

Made in the USA.

.3.5 oz/sqyd Mesh

This is the mesh that we use on our backpack's center pockets. It has a relatively light weight for mesh, while being difficult to tear. It can withstand getting caught on branches and other typical abrasion that backpacks are subjected to. The hole size is a about 4 mm (a little over 1/8"). 

 3.5 oz/sqyd (119 g/m²)

5.3 oz/sqyd 3D Spacer Mesh

This mesh has a three-dimensional structure which allows airflow and adds cushioning. It has a tricot backing so you can't see clear through the holes. We use it on the underside of our backpack's shoulder straps and belts to absorb sweat, add cushion, and add grip. Our 3D mesh weighs less than most other types.

 5.3 oz/sqyd (180 g/m²)

 About 3/32" (2.5 mm)

Torso Height:

To measure your torso height, you will need the help of a friend and a string or cloth tape measure.

Most hikers wear their belt near the top of their hips, however, it isn’t uncommon for hikers to position their belt higher or lower.

To ensure you lock in the perfect fit, we suggest putting a belt on over your clothes in the spot where you’d like to belt to ride. Start your measurement at the center of the belt where it meets your spine.

Lower your chin towards your chest.  This will cause the C7 vertebrae to protrude at the base of your neck. The C7 vertebrae will mark the top of your torso height measurement.

Using the string or cloth tape measure, follow the curve of your spine up from the center of your belt to your C7 vertebrae.  This measurement is your torso height.

Belt Size:

The padded portion of the belt is 1" shorter than the listed minimum adjustment. For example a "Medium (30-36 inches)" belt has padding which measures about 29" tip to tip, and has a minimum adjustment circumference of 30". It is the recommended size if your actual measurement is up to 36" however the webbing extends further.

To measure your belt size, pull a string or cloth tape measure tight around the spot you’d like your belt to ride. Choose a belt with a minimum adjustment of a couple inches smaller than your actual waist measurement. This will leave room for you to tighten down the belt if you lose a little weight on trail.

The belts on our Arc Series packs are also removable and interchangeable. This will give you the ability to switch the belt out if your waist size changes or if you order the incorrect size by mistake.

Click here for full instructions on how to wash our Dyneema® Composite Fabric backpacks.

Customer Reviews
4.9 Based on 135 Reviews
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Tyler J.
United States United States

Preposterously good

I’m 5’11”, 180lbs. Used to wearing a medium or large everything, but the medium arc blast was huge on me - the top bar of the frame was behind my ears. So i stuffed it back in the box and exchanged it for a small, which fits me perfectly. The mesh pouch fits my groundsheet and rain gear well. Tough to get bottles in and out with one hand, neigh impossible. Pack construction is flawless. Velcro doesn’t snag on material like i thought it might.

Tom S.
New Zealand New Zealand

NZ Tramp

Great first outing - Milford Track NZ, super low-fuss and the adjustment options on the waist belt meant the load was really well distributed. Looking forward to the next trip

Scott C.
United States United States

Light but some durability issues.

I used a black arc blast for our (wife and I) 2021 thru hike. Overall, I think I would choose this pack again, but it is not without some issues. The good - Very, very light weight. I used this as my slack pack because it was lighter than the packs the shuttle drivers let you borrow. - Below 25 pounds, comfortable to wear and distributed weight well. - Good range of adjustments to perfect fit for you. - When I had issues, customer service was phenomenal. Tips to consider - Don't get black. I could see very little in this bag. When I looked in other packs of the blue color, light made it through, and you could see inside. - I used the sizing guide they suggest, and this pack was almost too small for me. My wife's was too small and we didn't have time to get a new one from Zpacks, so she used a more conventional pack from REI. My tip is to go to the bigger size if you are close to the top of the range they give in their sizing instructions. Also, order your pack well in advance to give you time to work issues. When I say well, I am talking 6+ months. The issues (I won't say bad) - It is not waterproof. It is definitely resistant the entire trek, but virtually from the beginning a small amount of moisture would get in the bag during any substantial rain. Having a liner bag saved my stuff from ever getting wet, but there was almost always some moisture between the liner and the blast (when it rained). I believe the rain comes in 2 places - first is a for sure - abrasions, pokes, etc serve as entry points. I would say my bag itself made it through with minimal damage to the bag (talking the material, not the frame) and I could see little pinpoints of light inside the bag when I shined a bright light on it. The second thought is the seams. I don't know if it comes in, but I didn't seam seal, so not sure. - Not comfortable over 30 pounds and unusable at 35 pounds. The company says it can carry up to 35 pounds. It carried it, but not comfortably. It is very comfortable at 25 pounds (I frequently didn't even notice I was wearing it), but above that it started becoming less comfortable until 30 pounds where it was definitely uncomfortable. The straps dig in and it feels like the weight distribution is off. I heard from multiple people on the trail the same experience. Remember food can get pretty heavy, so keep this in mind as you look at your base weight. If you think you will routinely be at 30+ pounds, this isn't' the pack for you (in my opinion). - Durability is an issue. I had four damage issues with this pack during my hike. About halfway the vertical stay snapped. I was wearing and it just snapped. I did not fall or drop the pack when it broke (true for all damage issues). Not saying I never fell. Of course I did and perhaps that contributed, but that is part of hiking. This immediately turned it into a frameless pack and put a lot more weight on my shoulders. The good news was customer service was extremely prompt and I had a replacement in 3 days. About 75% of the way through my belt horizontal stay broke. When I took it off, I noticed the belt fabric (where the stay goes) was more than 50% worn through. I moved the stay from the top to the bottom and this helped keep the weight on my hips until the replacement stay and belt came (again quickly). Finally, where the belt stay connects on each side, one side tore through so the stay would work its way through while I was hiking and thus come out on the other side. This happened in my last 2 weeks, so I just put a safety pin through the webbing that holds the stay (not through the stay, but to keep it from coming through the webbing pocket), but this is not something customer service could fix without a complete pack replacement. Would I use this pack again? I probably would, but the "probably" is why I gave it 4 stars.

Ann F.
United States United States

Kid at Christmas

My husband is thrilled with his new Blue Arc Blast 55L. With 50 + years of backpacking under his soles, he's excited about the design, weight and color. Test run this weekend.

Dan K.
United States United States

Super light

Haven’t tried it on the trail yet, but my test load was comfortable around the house. Can’t wait for the first trip.