The ZPacks Arc Blast 55 is a dream for the ultralight gear aficionado. It is customizable, lightweight, and surprisingly comfortable - a testament to ZPacks and their level of intelligence and intent that is put into their designs.
The rating chart above shows where the Arc Blast ranks in overall performance amongst the other packs in our test.
The Arc Blast is custom built and allows you to choose from many options. We tested the 55-liter model with a medium torso length and a medium hip belt. Many micro adjustments that can be made to get this pack fitting just right — it should be known that this is a pack for expert gear fiddlers!
At 11 g/L max and stripped, this pack delivers the best average weight-to-volume ratio except for the frameless Granite Gear Virga 2. It's no contest; theArc Blast has one of the best weight-to-volume ratio for an ultralight backpack with a frame. We do want to warn against removing the frame from this pack, as it is more work than it's worth, in our opinion. The 5-piece carbon frame is tightly integrated into the pack itself and the frame is under tension, which makes the unit hard to remove. Other packs, like the Hyperlite Mountain Gear 3400 Southwest, have two aluminum stays making up the frame, which are much easier to remove and replace.
The Arc Blast has one of the best weight to volume ratios of any pack we've reviewed.
Load Carrying Comfort
The Arc Blast's load carrying ability is decent. The pack received a "great" score for carrying 15 lb loads and a "good" rating for 30 lb loads.
While we were surprised by the pack's performance when carrying heavy loads (30+ pounds), we do want to note that a pack of this size performs best with lighter loads. Compared to the super light, frameless Granite Gear Virga 2, the Arc Blast transfers medium weight loads to your hips much better. Compared to the ULA CDT, the Arc Blast scored higher regarding carrying comfort for heavier loads. The Arc Blast has a full frame, which transfers the load much better than the frameless CDT.
The Arc Blast has a full frame, which provides a lot of support and comfort for a pack of its weight.
This pack is best suited for folks with the experience (and budget) to carry a very light base weight. If your "heavy carries" are rarely more than the mid to low 20s, this pack is an excellent way to shave weight from your kit.
Though it skimps in many ways, the Arc Blast also provides ample padding in a few crucial places.
The Arc Blast pack is about as minimal as it gets in terms of features and is all about being lightweight when it comes to the design and construction. However, various (optional) features are available if you choose to add them to the basic configuration. Some of these add-ons include ice axe loops, trekking pole holders, and extra side pockets. The model we tested had an additional lumbar pad, and a V shaped top strap.
This seamed-taped waterproof fabric pack uses a roll top closure with Velcro and a buckle to complete its enclosed main pack, and the main exterior storage is a large mesh main pocket with elastic at the top. The side pockets are built with the same fabric as the main pack - with elastic at the top. They aren't as large as the ones on the Gossamer Gear Mariposa, but will only accept a one-liter Nalgene bottle. Like the Mountainsmith Scream 50, the waist belt tightens with two buckles on each side of the padded waist belt and has a very delicate zig-zag cord down each side which forms the compression system. The only additional external lashing points are two cords that allow you to secure a rolled foam pad horizontally to the bottom of the pack.
This small mesh panel is meant to provide air flow, but we found it to rest against the back without providing much ventilation.
The Arc Blast does not have a hydration bladder pocket inside but does have a small sewn-in loop for that purpose. You'll also find a center port to route the drinking hose over either shoulder. True to the minimalist construction, there are no D-rings on the shoulder straps and no whistle on the sternum strap buckle.
This large mesh pocket had one of the largest capacities of any pack we tested.
The Arc Blast 55 earned fairly low scores when it came to adaptability. The frame is complex, and we quickly realized how sorry we were to have disassembled this pack.
We rated the Arc Blast 55's compatibility with a BV500 bear canister "just ok." It fits vertically but packs poorly. A custom option of two over-the-top straps for securing the can outside on top is the best idea. The model we tested had only one over-the-top strap, making it difficult to attach a bear canister this way.
You may wish to remove the frame and waist belt on shorter trips, which can prove to be beneficial; we found that we needed to tie knots in the cords used to tension the frame. Throughout a long day, these cords slipped a bit through the cord locks that secure them, loosening the frame tension. Due to the slippage, a knot in the cord, or a safety pin, that acts as a positive stop against the cord lock, is necessary if you want to achieve the perfect frame and have it stay put. Finally, it is one of the least adaptable when it comes to load carrying comfort. Some packs, like the Exos and the Mariposa, work well with loads big or small, whereas the Arc Blast performs best with a load between 10 and 20 pounds.
The materials used in the Arc Blast are on par with the Hyperlite packs in terms of durability.
While this pack's hybrid Cuben fiber fabric (with a polyester face) is more durable than other non-faced Cuben fabrics, it is not as abrasion-resistant as the heavier nylon ripstop. However, this pack is designed for the user that prioritizes light weight over durability. You'll want to treat this pack's carbon frame with kid gloves; we avoided sitting on our loaded back or tossing it around with little care. Special care should be taken when packing, as the fabric is particularly fragile when metal objects (such as the edge of a carbon bear can) are pressed against it for extended periods. Much like the Hyperlite Mountain Gear Southwest 3400, we found that abrasions occurred when we did not sufficiently pad our bear can.
The Arc Blast 55, with its class-leading low weight, is best used by experienced ultralight backpackers. Two of our testers, who travel with seven to nine-pound base weights, have used this pack for thousands of miles while thru-hiking - and loved it. If you've logged the mileage to know exactly what feature set you need and want, and you're interested in the lightest pack with the most custom options, we'd recommend the Blast. While other packs were more comfortable when carrying loads into the mid and upper 20s, many experienced users feel this pack is "comfortable enough" for those heavier loads.
Retailing for $325, and even more if you want to add modular hip pockets or custom features, this is one of the most expensive packs we tested. We recommend it for experienced and expert ultralight backpackers who are willing to pay the premium to save ounces. Treated with care, this pack will last for many miles.
At $325, the ZPacks doesn't come cheap.
The ZPacks Arc Blast 55, which is a full half-pound lighter than any of the other top scoring ultralight packs, is our Top Pick for Ultralight Enthusiasts. If your total weight carried rarely exceeds 20 pounds, take a look at the Blast. The frame is a little tricky to adjust but carries well relative to the light weight. This is the pack you want if your primary desire is the lightest possible ultralight backpack with a frame.
Sizing, Accessories, & Other Versions
As with all products from ZPacks, the Arc Blast is available with myriad sizing options and custom components, both of which make it a perfect choice for the detail-oriented expert user. The pack is available in a variety of torso lengths, or adjustable torso length. Three waist belt sizes are available, as well as modular add-on hip belt and shoulder strap pockets. Just about any add on you can imagine is available, including straps specifically designed to carry a bear canister on top of the pack.
The ZPacks Arc Haul is nearly identical to the Arc Blast, but only built in the 60-liter size and with heavier Dyneema X Gridstop nylon fabric. It is a better choice for loads above the mid-20s and will better fit a bear canister inside the pack.