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Mountainsmith Zerk 40L Fastpack Review (First Looks)

Photograph: Mountainsmith The Zerk 40L Fastpack

The Zerk 40L Fastpack represents Mountainsmith’s first stab at an ultralight backpack aimed specifically at thru-hikers doing huge mile days with few breaks. Impressed by trail operating packs, the Zerk is designed to provide you entry to food, water, and essential gear while being cozy enough to go away on all day. The design is centered around large, thick shoulder straps and a detachable foam framesheet.

Mountainsmith designed the Zerk in collaboration with thru-hikers, specifically Mountainsmith athlete Tom “The Real Hiking Viking” Gathman. Such partnerships can typically really feel like advertising gimmicks, however I had purpose to consider that Mountainsmith takes this stuff significantly. I’m knowledgeable photographer/videographer, and the Mountainsmith Tanuck 40L, designed with photographer Chris Burkard, is my all-time favorite digital camera bag because it seems like a backpack designed by a photographer.

Going into this initial First Appears assessment, I hoped that the same “on the front lines” design and execution would spring from the collaboration between Mountainsmith engineers and the thru-hiking group.

With all this in mind, I took the Zerk out for a quick two-day, one-night cross-country skiing excursion in the japanese Sierra Nevada.


All the things pictured right here, minus Bothy the Cat and the trekking skis, discovered a spot inside or outdoors the Zerk 40L. The Zerk is a well-organized pack, notably with regard to its external pockets and lashing techniques.


  • Large, comfortable shoulder straps
  • Dual mesh shoulder pockets with drawstrings
  • Shallow, diagonally reduce aspect pockets
  • Outer secondary mesh aspect pockets
  • Broad roll-top enclosure with over the top webbing
  • Giant entrance stretch pocket
  • Elastic gear attachment factors situated high on shoulder straps
  • Integrated shoulder-strap safety whistle
  • Stabilized with a two-piece Atilon and EVA foam panel (no body sheet or stays)
  • Detachable non-load bearing waist belt
  • Detachable bear-can straps with a number of attachment factors
  • Detachable reflective front bungee
  • Hydration system port and inner attachment


  • Dimensions: 18.5 x 11.75 x 5.75 in (47 x 30 x 14.6 cm)
  • Weight (including all straps and waist belt): 28 oz (793.78 g)
  • Really helpful load: Up to 30 lbs (13.6 kgs)
  • Quantity (principal compartment, extended): 40 L
  • Quantity (foremost compartment, compressed): 32 L
  • Pack Material: 100D Nylon HT w/ 200d Spectra Double R/S TPU
  • Foam Material: Atilon, EVA, and PE
  • Mesh Materials: 201g / 320 g Stretch Mesh
  • Compression Straps: 10mm webbing
  • MSRP: $219.95


  • Superior external organization: with good planning, you possibly can hike all day and by no means take this pack off.
  • Shoulder straps are broad, snug, and safe.
  • Shoulder strap pockets are nicely positioned, giant, and maintain gadgets securely.
  • Aspect pockets are minimize diagonally, allowing you to succeed in water bottles easily.
  • Foam stabilizing again panel is snug and seems to breathe properly.
  • The brilliant orange, reflective accents are a pleasant security contact.
  • The “designed by a thru-hiker FOR thru-hikers” factor feels real.
  • A mass-produced minimalist pack with cottage business features.


  • Shallow, diagonal reduce aspect pockets don’t maintain bottles securely.
  • Removable bear-can attachment straps are arduous to get on and off.
  • Compression straps appear to tug a bit “sticky”.
  • Stitching on one of many mesh pockets is already coming unfastened: worrisome for a pack that is constructed to final for hundreds of miles.
Product Mountainsmith Zerk 40L Granite Gear Crown2 38L
Dimensions 18.5 in x 11.75 in x 5.75 in (47 cm x 30 cm x 14.6 cm) 22 in x 14.75 in x 7 in (55.9 cm x 29. 84 cm x 17.78 cm)
Weight 28 oz (793.78 g) 33.5 oz (950 g)
Quantity 40 L (prolonged), 32 L (compressed) 38 L
Steered Load 30 lbs (13.6 kgs) 35 lbs (15.87 kgs)
Load Lifter straps No sure
Body Detachable dual layer Atilon and EVA foam Removable PP frame sheet
Pack Materials 100D Nylon HT w/200d Spectra Double R/S TPU Robic Excessive-tenacity nylon (100D and 210D)
Inner Organization One compartment One compartment
External Organization Four aspect pockets, four shoulder strap pockets, one rear mesh pocket, detachable bear canister webbing, removable lashing bungee Two hip belt pockets, two aspect mesh pockets, one rear mesh pocket, removable lid with pocket
Closure Type Roll-top with over the top webbing Roll-top with excessive webbing
Hip Belt Removable, non-load bearing Detachable, load bearing with pockets.
MSRP $219.95 $184.95

The Zerk’s features are most commonly found on cottage business packs (the shoulder strap pockets and diagonal aspect pockets remind me of our current evaluate of the Atom). Likewise, the worth level and weight are just like the basic Gossamer Gear Mariposa. For the upcoming Gear Review, I’ll remember to do in-depth comparisons of the out there cottage business frameless and minimalist packs. However for this brief evaluate, I needed to match the Zerk to a different mass-produced pack of an analogous weight, quantity, inner group, and load capacity – the Granite Gear Crown2 38L.

The manufacturers promote both packs as slimmed down choices aimed at the ultra-light crowd. The Crown2’s quantity sits squarely between the Zerk’s compressed 32L volume and its extended 40L volume. It does so at the cost of about 5.5 oz (155.9 g) of weight. The Crown2 has a advisable load of 35lbs (15.87 kgs) versus the Zerk’s 30 lb (13.6 kg) capability. The Crown2 achieves this with a thick hip belt and a plastic molded removable frame-sheet.  Eradicating the body sheet will get Crown2 right down to 25.6 oz (754.1 g), 2.4 oz (68 g) lighter but significantly less secure than the Zerk.

The Crown2 makes a nod in the direction of accessibility with giant mesh hip-belt pockets, however aside from that has roughly the identical accessibility as many different mass-produced packs. The shoulder straps and hip-belt are business commonplace designs.

These options are why the Zerk stands out amongst mass-produced packs: trail operating inspired shoulder straps and a foam frame sheet that give it killer comfort-hauling chops for its weight class. Those same features permit for wonderful and weird (for mass-produced packs) pocket placement.

The Zerk 40L Fastpack is many things, however it isn’t a advertising gimmick. It feels just like the Zerk was designed by a foot-sore, achy-shouldered thru-hiker with nothing to do however daydream about how he would change his pack if he might. One thing to remember although: At 28 oz (793.78 g) the Zerk isn’t the lightest minimalist pack obtainable. It wasn’t made to be. It was designed to take a seat at a crossroads of consolation, accessibility, sturdiness, and weight.

This First Look will give attention to two of those parts: accessibility and comfort. An extended, extra complete Gear Review is forthcoming in summer time 2019. In that evaluation, I’ll elaborate on the elements mentioned here. At that time, I’ll also be capable of converse to the long-term sturdiness of this pack, in addition to make a extra in-depth comparison to other minimalist frameless packs.


The Zerk 40L Fastpack’s essential strengths are consolation and accessibility. Both are enabled by the broad trail operating inspired shoulder straps.

To start out with, the Zerk provides you easy access to often used pieces of drugs. Single compartment roll-top enclosures are widespread in minimalist packs, however the place the Zerk shines is its exterior organization. It has 4 well-placed shoulder strap pockets, two on every strap, with the higher pocket nesting inside the lower pocket. The top pocket cinches with elastic twine, making it best for securing electronics or small water bottles. The underside pocket is cinched permanently with elastic, and it’s roomy sufficient to hold snacks or different small items of drugs.

On my testing trip, I fit my Sony Rx100vi, my iPhone 6 and case, a can of bear spray, 800 calories value of snacks, a small pocket knife, headphones, and spare digital camera batteries within the shoulder strap pockets. All these things felt secure, and I especially appreciated understanding that my digital camera and telephone have been straightforward to succeed in but protected behind an elastic drawcord. Hikers with bigger telephones (or marginally larger cameras) should not have any drawback: the pockets swallowed each these gadgets with room to spare. If wanted, the shoulder-strap pockets might easily fit chapstick, a small tube of sunscreen, a lighter, a contact lens case, or different sundries on prime of all the other gadgets I’ve mentioned.


Large shoulder straps give plenty of area for deep, stretchy pockets. In this photograph, mine are holding a digital camera, additional batteries, 800 energy of meals, bear spray, my telephone and wallet, additional batteries, a pocket knife, headphones, and chapstick.

The Zerk has a detachable webbing system for bear-canisters or different cumbersome gadgets. I used it to attach my Nemo Switchback to the pack. I like this technique for 3 reasons. The first is that in case you don’t have any bulky gadgets you’ll be able to depart the webbing at house with out having to cut it off permanently. The second is that there are multiple attachment loops everywhere in the pack, supplying you with the pliability to attach gear the place you need to attach it. The third is that the webbing (along with the aspect compression straps, detachable bungee, and emblem) are shiny red-orange. The brand and bungee are reflective. Not only will this aid you discover your pack at the hours of darkness, but additionally they add an extra layer of security throughout searching season.


Detachable bear-canister webbing can attach at a number of factors (orange loops) or be eliminated utterly. I used the webbing to lash my CCF pad to the back of my pack.

The detachable bungee is designed to provide you extra lashing options for the surface of the pack. I can’t converse to its effectiveness as my pattern pack seems to have shipped without one. As soon as Mountainsmith sends me a bungee I’ll be capable of tackle its performance in my longer evaluation.

The twin aspect pockets are also value mentioning. The upper pockets are common from the same Spectra material as the remainder of the pack. They’re shallow and diagonally minimize, with the upshot being I might simply attain and substitute my 1L Smartwater bottles on the go. The downside? The bottles were not safe. They persistently fell out once I bent over to adjust my ski bindings or fetch a dropped trekking pole. I even lost a bottle totally within the deep snow by way of which I was skiing.

I discover the trade-off value it. But when your trek includes talus scrambling, bushwacking, or snowdrifts, regulate these bottles. You possibly can all the time use the aspect compression straps to secure gear that doesn’t have to be reached on-the-go.


Shallow, diagonal minimize aspect pockets give you easy access to your water bottles. The trade-off is water bottles that fall out once you bend over.

The lower aspect pockets are roomy, with an elastic band throughout the top for more safety than the upper aspect pockets. I used these pockets to carry lunch, trash, and a small bag of sundries and, just like the bigger aspect pockets, was capable of entry these things with out breaking my stride.

The back stretchy mesh pocket is giant, all the width of the pack. Aside from that it’s pretty commonplace — useful to retailer gadgets in, but not accessible while walking.

For this First Look, I ate all my snacks and lunch on the go, by no means taking the Zerk off during my eight-to-ten hour skiing days. I’m completely satisfied to report, with none exaggeration, that that is probably the most snug mass-produced pack I’ve ever worn. Properly designed, extra-thick shoulder straps and a cushty foam inner structure seem to be the contributing comfort elements. Will probably be value seeing how all that thick foam breathes as soon as temperatures warm up.

I used to be testing a number of different pieces of drugs, so I had some additional gadgets. My complete weight (including meals and water) came in between 24 and 28 lbs (10.88 to 12.7 kgs). Mountainsmith recommends a load no heavier than 30lbs, but even at these upper ranges, the pack was snug and secure. For my upcoming Gear Review I’ll overload the pack to determine its consolation at greater-than-recommended masses.

I observed two drawbacks to the Zerk throughout my preliminary testing. The primary is that I struggled with attaching and removing the optionally available bear-canister webbing, even with warm arms within the consolation of my house. Particularly, solely one of the attachment loops gave me problems. In an identical vein, the compression straps seem a bit “sticky” to tighten. We’ll see if each of this stuff loosen up with extended use.


For some cause, this specific loop gave me hassle. Time will inform if it loosens up or not.

The second concern I observed was certainly one of durability: a small amount of stitching around the elastic on the upper-right shoulder strap pocket appears to have come unfastened. A minor thing, so minor that it was troublesome to get a superb picture, and I finally decided to not. That being stated, it’s a tad worrisome after two days of use on a pack designed to last hundreds of miles per yr at 20, 30, and 40 miles a day (a paraphrase of the Mountainsmith advertising copy). Time will inform if this can be a one-off fluke or something that may occur to stitches elsewhere on the pack.

All in all, I’m highly impressed with this pack. Inside the first hour of my check, I shortlisted the Zerk as my pack of selection for my subsequent long-distance hike. It’s consolation, security, and well-designed exterior organization are all top-notch, especially for the worth point. I look ahead to testing its sturdiness and luxury over a more sustained interval.

  • The Mountainsmith Zerk 40L Fastpack can be out there to shoppers in July 2019. It is presently not out there for pre-order.
  • The Zerk has comparable features to the Atom by Atom Packs. You’ll be able to learn an in-depth assessment of that wonderful pack here.
  • Going frameless? Here’s some recommendation from our forum.
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