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ZPacks Blast 18 Backpack Review

At less than four ounces and roomy enough for a weekend of SUL gear (30L), the ZPacks Blast 18 certainly qualifies as "SUL" by the standard set several years ago by the Gossamer Gear G6, but is far more durable (yet has a similar weight as the first G6).


Overall Rating: Recommended

The Blast 18 has everything I want in an SUL weekend pack: durable fabrics, light weight, plenty of capacity extended with outside pockets, and a simple design. The Cubic Tech CT5K.18 fabric is durable, abrasion-resistant, non-absorbent, and offers good seam strength for carrying heavier loads on occasion. The pack could use improved styling, packbag shaping, and finishing, and because it is offered with a drawcord closure, I'd recommend at least offering the option of a sewn-in top flap and/or top pocket for further weather protection and storage space. Relative to its key competitors, the Gossamer Gear Murmur and the Mountain Laurel Designs 2009 Revelation, the Blast 18 competes effectively. The choice of fabric elevates the cost of this pack to a price point $25 higher than the Murmur, and the inexperience in manufacturing and design places it in a styling class one notch below the Revelation. However, if you are looking for an SUL pack that effectively carries a small load for ultralight backpacking with less than 15 pounds, the Blast 18 serves the purpose admirably.

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by Ryan Jordan |


There are two problems with the SuperUltraLight ethic.

The first is that it motivates SUL aficionados to develop throwaway gear that may last a season, if you're lucky. I once used a tarp made of an extremely light Cubic Tech fabric (CT0.3.K08, at 11.4 gsm) that blew up in one unfortunate midsummer wind gust in the shadows of the Tetons, while camping at the uppermost campsite near the treeline in the North Fork of Cascade Canyon. And my every attempt to manufacture, take care of, and otherwise use so-called "SUL" packs (including spinnaker versions of the Mountain Laurel Designs Prophet and Gossamer Gear Uberlite G6) made with lightweight spinnaker nylons, polyesters, and Cuben Fibers, has resulted in failure of the fabrics at the seams caused by repetitive stress.

I think SUL gear such as this can serve specialized purposes for the casual hiker, for the hiker who might not care about disposing (and replacing) gear on a regular basis, or for the hiker interested in saving every gram of weight possible for a single expedition (e.g., Andrew Skurka used an ultralight Cubic Tech tarp on his Great Western Loop trek, and I used a Cuben Tech pyramid shelter for the Arctic 1000).

The second problem with the SUL ethic is that it motivates people to apparent insanity, by which every possible bit of function and durability is sacrified for the sake of meeting a weight spec. I'm speaking a bit tongue in cheek about this insanity of course, since I seem to be a regular participant and proponent of it, but I do increasingly value that elusive and ill-defined metric we call the "performance-to-weight ratio".

That's why I was pretty excited when I took my new ZPacks Blast 18 backpack - a heavy duty Cubic Tech weekend pack that weighs a scant 3.3 oz - out of its mailing envelope...

ZPacks Blast 18 Backpack Review - 1
The ZPacks Blast 18 is made from a stronger, heavier Cubic Tech fabric (CT5K.18), bringing abrasion resistance and strength to SUL packs without adding much weight. The base model as configured here weighs only 3.3 oz.

Durable SUL

Joe Valesko, the designer of the Blast series and the owner of ZPacks, made a prototype out of the same fabric (CTK5.18). He put it to good use, completing the 2,600-mile Pacific Crest Trail with it in 2007.

At less than four ounces and roomy enough for a weekend of SUL gear (30L), the ZPacks Blast 18 certainly qualifies as "SUL" by the standard set several years ago by the Gossamer Gear G6, but is far more durable (yet has a similar weight as the first G6).

So, what might differentiate the Blast 18 from other SUL packs is its durability. Instead of the sub-30 gsm Cubic Tech variants found among manufacturers promoting SUL tarps, stuff sacks, and other gear, the Blast 18 uses Cuben Fiber 5K.18, a 48.4 gsm fabric with a stiff hand that gives the pack robust shape, waterproofness, and outstanding durability in both seam strength and abrasion resistance.

About the Fabric

The primary problem with the use of Cuben Fiber in outdoor gear is its seam strength. The fabric is better characterized as a plastic film reinforced by a low-density fiber matrix than conventional woven outdoor gear fabrics, which are typically high density wovens reinforced by waterproof coatings and/or calendaring.

Cubic Tech CT5K.18 is far more durable than its ultralight cousins (e.g., the model CT2K variants) primarily because of its weight, film thickness, and higher fiber density than CT2K.08.

The bottom line is that CT5K.18 has good tear strength (190 lb/in, vs. 105 lb/in for CT2K.08). And, while I don't have data for seam strength or abrasion resistance, my field testing and inspection of seams under load indicates that CT5K.18 may actually be suitable for long term use and thru-hiking. Don't expect a miracle, however: this fabric is still considered ultralight and won't perform to the strength standards of most heavier woven fabrics. Seams will fail over time if you consistently pack heavy loads in a pack like this (I found seams starting to separate in response to the all-day stress of hiking with 35-lb loads), and the fabric is more subject to punctures from sharp things (e.g., thorns and deadfall), more so than woven nylons such as the 210 Dyneema grid ripstops that have been popular in packs by ULA and others.



1800 cu. in.


3.3 oz (Base Model)


$105 (Base Model)


Cubic Tech CT5K.18

  Shoulder Strap Padding:

1/4" Closed Cell Foam


  • Nonelastic drawcord top closure
  • Two side water bottle pockets with elastic closure
  • Large rear pocket with elastic closure integrated with top side drawcords for compression and securing gear
  • Frameless design, no back padding or other structure
  • Padded shoulder straps
  • Optional build-to-order features are available for extra cost and weight. For example, a full featured pack containing a padded wing belt with belt pouches (1.9 oz, $39), sternum strap (0.3 oz, $6), shoulder strap daisy chains (0.2 oz, $8), hydration port ($4), hydration sleeve (0.3 oz, $10), outside shock cord loops that could secure a sleeping pad or tent horizontally (0.4 oz, $7), shock cord compression system (0.4 oz, $9), top strap (0.4 oz, $9), haul loop (0.4 oz, $2), one ice axe loop (0.1 oz, $4), sleeping pad sleeves (0.5 oz, $20), two shoulder pouches (0.6 oz, $28) would come to a weight of 8.8 oz and cost $251.

ZPacks Blast 18 Backpack Review - 2
My favorite "I can't believe I didn't think of that" feature of the Blast 18 is the circumferential compression cord that serves three functions: a strap for securing tall gear extending from the pockets (such as trekking poles), load compression for the upper part of the pack, and the elastic closure for the top of the back pocket.

Load Carrying Capacity

ZPacks Blast 18 Backpack Review - 3
The base model of the Blast 18 does not include a hip belt, has a narrow profile, and rides high on your back (the nature of most small packs). This creates a bit of bob and wobble, but padded shoulder straps, the narrow design, and high center of gravity makes "heavier" loads (less than 15 lbs) more comfortable than belt-less packs that are fat and short, and ride low.

Assessing the load carrying capacity of a frameless pack, especially one without a waist belt, is sort of a silly exercise. Your ability to carry a load will depend primarily on the strength and conditioning of your trapezius and deltoid muscles. Most casual hikers have not conditioned these muscle groups in a way that is optimized for carrying a heavy load in a frameless pack. In other words, you condition the muscles by carrying the load. My experience tells me that most folks will find 15 pounds acceptable for long distances (e.g., more than six hours of hiking per day), and 20 pounds acceptable for short distances (a few hours of hiking per day). Those with well-conditioned shoulder muscles can usually accomodate 25 to 30 pounds for short distances and 20 to 25 pounds for long distances. Thru-hikers who have been on the trail for several weeks with a frameless pack may find 35 pounds, or more, acceptable at both short and long distances.

ZPacks Blast 18 Backpack Review - 4
Short shoulder straps on a small pack means that it rides high on your back, which I prefer for small volume packs that do not have a hip belt. It keeps the center of gravity high, which relieves back strain, but demands more from your trapezius and deltoid (shoulder) muscle groups.

I could never recommend a previous SUL pack such as the Gossamer Gear Uberlite (G6) or the Mountain Laurel Designs Prophet 40 (Spinnaker Version) with weights greater than 25 pounds over long distances and durations. However, I think the Zpacks Blast 18 (even at a similar weight as the other two) would be up to the task, and I'd have no hesitation recommending it for the thru-hiker interested in tackling a Triple Crown Trail, assuming they were intentionally careful with their gear.

Volume Capacity

Eighteen hundred cubic inches is not a lot of capacity.

It's generally accepted by our community that it's just enough for a day or two of food and a simple, ultralight kit of summer gear. My summer ultralight kit easily fits into the Blast 18 without overcompressing insulating gear, and in addition to three days of food, includes a 30-degree synthetic quilt, a torso-sized inflatable sleeping pad, a breathable bivy sack, synthetic insulated jacket, rain jacket, rain pants, a two-person tarp, solo cook kit, and other basic essentials. I keep a windshirt in the back pocket, a water bottle in a side pocket, and lunch in the other side pocket.

In the photos for this article, the Blast 18 is packed with a spring kit for snow cave camping, and includes a 20-degree down sleeping quilt, synthetic insulated jacket and pants, an eVENT bivy sack, a TorsoLite pad, a 3/4-length 5mm foam pad (folded and placed against the back panel), a liquid fuel stove and 1.3L pot, and 1.5 days of food, in addition to basic essentials. My snow shovel and wind jacket (which I'm wearing) go in the back pocket, while food, fuel bottle, and a water bottle get stashed in the sides. The insulation of my sleeping bag, jacket, and puffy pants gets a little more compressed with my spring snow kit, but not enough that I have concern about damaging the insulation.

The outside pockets of the Blast are generously gusseted, so they expand sufficiently for the stowage and retrieval of gear without feeling like you are stuffing your hand into a jar of pudding to find something. The back pocket was plenty big enough to stuff the body of a solo single wall TarpTent into, and the side pockets expanded to easily accomodate a full two-liter Platypus bottle.

ZPacks Blast 18 Backpack Review - 5
Gusseted pockets provide plenty of width for the stowage of bulky gear, but not much height. I was not comfortable putting in a tall, 2-liter Platypus bottle in the pocket, and it ended up coming out of the pocket while bushwhacking. I didn't really see this as a disadvantage of the pack, so I simply changed my style accordingly and switched to a shorter water bottle. On this trip, I used one packet to pack my lunch and fuel canister (a large Powermax canister), and the other pocket for my water bottle (a 600ml Evernew bottle).

While marketing on the ZPacks website suggests otherwise, items are easier to retrieve out of the side pockets while on the trail than to put back, because of the elastic pocket closures. However, this is no fault of ZPacks in my opinion, but a flawed expectation of the user. With a pack like this, swinging the pack off your back (even while walking, if you have to) and grabbing something out of the side pocket is such a trivial exercise that to belabor the need to access side pocket gear while on the go seems to reflect fundamental incompatibilities with the ultralight ethic. This isn't adventure racing, this isn't an adventure racing pack, and it's not going to be loaded with enough gear that stopping for a moment to remove the pack shouldn't provide great amounts of disruption to your wilderness experience. If it does, then there may be other problems that have nothing to do with the pack!

ZPacks Blast 18 Backpack Review - 6
When hiking with a pack that weighs only 10 or 12 pounds, swinging the pack off and grabbing the water bottle out of it, rather than inventing new yoga positions to retrieve the bottle from a side pocket, is a preferable modus operandi for me. There is something aesthetically satisfying about tossing a pack on and off your shoulder when everyone else is struggling to load their behemoths to their body.

The Blast 18 will provide enough capacity for overnights and weekend trips for the hiker willing to keep their kit simple and compact, but some discipline will be required in the selection of bulky gear, because volume is limited.

A Note About Packbag Shape and Dimensions

ZPacks Blast 18 Backpack Review - 7
The Blast 18 is symmetrical and uniform, making it an ideal pack for rolling a sleeping pad inside for virtual frame structure. My preference is to fold the pad and wear it against the back panel for padding and to provide some shape that gives the pack more contact surface area with your back, which feels better for carrying heavier loads.

The Blast 18 is a nearly perfect cylinder, which makes it an ideal pack for those that like to pack a foam sleeping pad as a cylinder inside the pack, then stash gear into the middle of the cylinder. I'm personally not a fan of this configuration, but have to admit that unlike most other "shaped packbag" packs that are not cylindrically symmetrical, this configuration works well with the Blast 18. As noted below, depending on perspective, you might find this packbag shape appealing or a liability.

In addition, the Blast 18 carries both small and overstuffed loads well (i.e., a load where the top collar is fully extended, as in the photos), because it maintains a thin, tall shape that does not ride low on the back (an important characteristic of a pack without a waist belt).

Final Analysis

What's Hot

  • Durable but ultralight fabric.
  • Simple, symmetrical design.
  • Gusseted outside pockets provide easy access and meaningful capacity.
  • Compression integrated into back pocket closure provides gear security on the sides of the pack as well.
  • Drawcord closure provides better volume utilization for the weight over roll-top models.

ZPacks Blast 18 Backpack Review - 8
It doesn't get any simpler than this: a drawcord closure provides the best utilization of packbag volume for the weight, allows for fast and easy access to the packbag, and requires little trim and hardware. Unlike a rolltop closure, however, the drawcord style suffers from lesser protection from precipitation, something that could easily be alleviated if the pack had an option to add a sewn-in top flap or pocket. I dealt with the limitation simply by stowing my gear (as you probably will anyways, regardless of closure type) in waterproof bags. Even in heavy precipitation (rain and wet snow), I never really missed having the roll-top, which surprised me.

What's Not

  • Add-on options provide custom build-to-order pack to suit needs but can result in a very expensive pack and can more than double the weight of the base model.
  • No option for a top pocket or flap to extend storage and/or keep water/snow out of the drawcord closure.
  • Drawcord closure string is extremely thin and may cut fabric of extension collar over the long term.
  • Construction techniques and styling reflect classic young cottage "garage manufacturing". The quality is high and the pack is well sewn, but makes use of simple construction techniques that limit shaping and styling options.

Market Comparison

I think it's important to consider the ZPacks Blast 18 in context with its primary competitor, the Gossamer Gear Murmur (Mountain Laurel Designs was not manufacturing a sub-30L SUL pack at the time of this writing, but they were offering a more richly-featured pack also made with Cubic Tech CTK5.18, the 2009 Revelation, which is heavier and more durable than the previous 2006 model that we previously reviewed).

Manufacturer/Model Packbag Volume Weight Relative Durability Suspension Other Features Price
ZPacks Blast 18 1800 cu. in. 3.3 oz  Excellent (1.5 osy Cubic Fiber CT5K.18) padded shoulder straps two side pockets, one back pocket, drawcord closure $105
Gossamer Gear Murmur 1700 cu. in. 7.5 oz Fair (1.1 osy nylon spinnaker) padded shoulder straps, webbing waist belt two side pockets, one back pocket, rolltop closure, pad sleeve, $80
Mountain Laurel Designs 2009 Revelation 2000 cu. in. 6.2 oz Excellent (1.5 osy Cubic Fiber CT5K.18) padded shoulder straps, winged hip belt, sternum strap two side pockets, one back mesh pocket, rolltop closure, cord compression $170

The relative strengths of the Blast 18 are its weight and durability, while the Murmur offers more features at a lower cost. The Revelation offers greater capacity, more refined styling, and when compared to the scenario of adding options to the Blast 18 that match the features of the Revelation, the Revelation comes in slightly less expensive.

Unfortunately, I find it hard to justify spending more than $100 on such a small pack that requires little in the way of sophistication to effectively carry light loads, but in the absence of other options, my personal choices do lean towards the more durable packs, because I'm more confident of their longevity, an important consideration for me as I continue to pursue a lighter and simpler lifestyle.

ZPacks Blast 18 Backpack Review - 9
The very simple construction techniques of the Blast 18 are both functional and effective, but lack the refined styling and aesthetic of more evolved packs that use more sophisticated manufacturing techniques.


I found myself not wanting much after using this pack. I did replace the drawcord closure with a thicker string because I have found very thin strings abrade and cut through Cubic Tech fabrics over time. The weight penalty for replacing the string was negligible.

ZPacks Blast 18 Backpack Review - 10
The ultra-thin drawcord that ships with the pack feels like a cutting wire. I ended up replacing it with a thicker (2mm) cord, which not only alleviated my fears about the cord cutting into the Cubic Tech fabric, but it made it easier to use while wearing gloves or mittens.

My only complaint with the pack is in its packbag shape. While the sausage design (symmetrical cylinder) works well for enclosing a rolled-perimeter sleeping mat (into the center of which gear is stowed for stability), it's not particularly stylish and doesn't rest against your back when fully loaded as well as it could. Carrying the Blast 18 stuffed to its gills feels a bit like hauling a log on your bag (albeit a soft, light one), because it does sort of roll and bobble here and there. I was able to mitigate this effect somewhat by folding my foam pad into thirds and using it as a virtual frame against the back of the pack, but for this to work most effectively, I would have prefered a slightly wider packbag. In addition, I'm a fan of packbags that taper from a smaller cross section near the bottom to a larger cross section near the top, because they accomodate widely varying load capacities a little better (although, this is less of an issue with such a small volume weekend pack like the Blast 18).

Photos: Ryan and Stephanie Jordan; Olympus E-510 Leica Summilux 25mm/f1.4.


"ZPacks Blast 18 Backpack Review," by Ryan Jordan. (ISSN 1537-0364)., 2009-05-19 00:05:00-06.


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ZPacks Blast 18 Backpack Review
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Steven Evans
(Steve_Evans) - MLife

Locale: Canada
Re: packweight should vary depending on the goals of the trip on 06/03/2009 09:44:42 MDT Print View

I see where you guys are coming from, but there are people who definitely like to go as light as possible 'most' of the time, even for an overnighter. As a matter of fact, I usually hit the trails for only a night when going really light to test conditions against gear - I have yet to complete a Sub 5lb trip longer then 3 days but hope to this summer.

It also depends on personal comfort. What I consider to be comfortable may be pure agony to others and vice versa. For summer where the temps are nice, I would have a hard time bringing MORE then 6-7 pounds...unless I'm with my girlfriend, which doesn't count because the red wine alone is enough to break a gorillas back. :)

Sooo, since this is the Blast 18 review, I'll just say that this pack has a market - I've got the 24 version, and a number of people on this site also own them. It's got to be one of the most feature (all optional) rich packs at such a low weight.

Einstein X
(EinsteinX) - F

Locale: The Netherlands
Re: Re: packweight should vary depending on the goals of the trip on 06/04/2009 10:45:45 MDT Print View

"Sooo, since this is the Blast 18 review, I'll just say that this pack has a market - I've got the 24 version, and a number of people on this site also own them. It's got to be one of the most feature (all optional) rich packs at such a low weight."

Oh I definetaly agree that there's a market for the Blast packs. I own a GG whisper and what I don't like about it is the lack of pockets on the thing. So if I'd be looking for a new SUL pack I'd definitally have a look at Z-packs. I'm still not sure about Cuben fiber tho, for some reason a woven fabric seems more natural than a fiber reinforced film. I would however love to take a CF Blast on a hike. Can someone lend me one???


te - wa
(mikeinfhaz) - F

Locale: Phoenix
i thot SUL meant "six ul packs" on 06/04/2009 11:07:11 MDT Print View

but Eins, how can you have just one SUL pack? you need six of them!

for instance... i have a Blast 16 that i use for low weight, low bulk kits. but for high bulk, low weight it doesnt have the room for my un-stuff-sacked quilts. (i like to let 'em loft up inside the pack-adds potentially years of life believe it or not)
for the high bulk trip, i may use either the Conduit or the Fanatic Fringe Thompson Peak. FF makes a smaller pack called the Alpine Trail @ 6 ounces if you cannot make the leap to Cuben.

Einstein X
(EinsteinX) - F

Locale: The Netherlands
Re: i thot SUL meant "six ul packs" on 06/05/2009 04:36:51 MDT Print View

"but Eins, how can you have just one SUL pack? you need six of them!"

Oh yes I agree, but it all has to do with the $$$. This month I bought my 13th pack (I think, could also be my 14th); a really nice Osprey travel bag (with wheels) cuz I needed wheels for my job. And since at the moment I don't need a new hiking pack and really really needed wheels the Osprey got priority. However for this years fall hike I do need a lighter 4 nights/5 days pack,my standard light kit. It should be a lighter version of my home made pack, which you can see in my avatar pic <<==. But I will have to make one, cuz my specific design is not on available on the market, but I'm affraid I won't have (or want to make) time for making a backpack. This job is taking up too much time :(


Steven Evans
(Steve_Evans) - MLife

Locale: Canada
Re: Re: i thot SUL meant "six ul packs" on 06/05/2009 07:53:19 MDT Print View

This month I bought my 13th pack

You have 13 packs but no z-pack blast!?!? Shame on you Eins.... ;)

Edwin Short
( - F
Z pac on 06/08/2009 21:40:24 MDT Print View

I have one that I modified (I always modify!) added a about 12 in collarn now I tie a simple overhand knot to close, water tight and increased capacity, I took thelarge back pocket off, (I hang my tarp and raingear off the bottom, I seam sealed all the seams, now it is fairly close to water resistant. other than thaat a great light and tough pack. most folkd don't believe how tough cuben is! gnome

jeffrey rumbles
(jsrumb) - F

Locale: southern, ca
Blast 18 on 08/28/2009 07:49:44 MDT Print View

I have been using my blast 18 with hip belt for about a year and a half now. It has been on trips between one and four days duration, with quite a bit of bushwacking thrown in. I have been very impressed with the comfort and durability of the cuben fiber. My wife has the same pack in sil-nylon and it has not fared as well(but the stitching is doing fine!).
Joe (z-packs) was a great help in the purchase process, and always had the time to answer my questions.
Z-packs has won my future business, and my recommendation!

Dan Durston
(dandydan) - F

Einstein on 10/24/2009 22:43:29 MDT Print View

I am not SUL, but a cuben fibre pack appeals to me because having a heavier pack does pretty much nothing to increase my enjoyment of the trip. A heavier pack might be more durable, but at the kind of weights I am carrying it won't be significantly more comfortable. So would I rather carry an extra pound so my pack lasts longer? Or would I rather carry an extra pound of luxuries like fresh foods or spirits? As long as the pack is reasonable durable, I will choose the lighter pack and extra luxuries.

These 1.5 cuben packs seem to be a great blend between durability and lightweight. I do not want disposable gear, which I why I'm glad to hear that with reasonable care 150 days should be achieveable. That's quite a few years of hiking for me.

Edited by dandydan on 12/09/2009 22:38:05 MST.

Jeff Antig

Locale: Pacific Northwest
Re: Einstein on 10/25/2009 01:08:04 MDT Print View

Hopefully this material is considerably stronger than regular cuben fiber. I'm not a big fan of cuben fiber because it is so thin that it makes me nervous. That being said, I would still buy the pack if it was made looks very easy to DIY as it is now.

Jim Colten
(jcolten) - M

Locale: MN
Re: Einstein on 10/25/2009 07:16:12 MDT Print View

Hopefully this material is considerably stronger than regular cuben fiber.

Cuben Tech lists about 30 different product weights, almost all of them heavier than the products typically discussed on this forum. The 1.5oz/sailmaker's-yard stuff used in Zpack's Blast packs is tough stuff. I wouldn't hesitate to use it in a pack.