ProView – Mountainsmith Zerk 40

Loaded with quick access features, the Mountainsmith Zerk 40 enables you to do more, with less time.

The Mountainsmith Zerk 40 pack kept up with me on a 14-hour 32-mile peak-bagging mission in the remote Pasayten Wilderness in Northeastern Washington. We felt super light as we cruised through 10’s of trail miles and scrambled through 1000’s of feet of talus. Ultimately tagging three of Washington’s highest summits in one quick trip.

Mountainsmith Zerk 40

Product Description: Countless hours, thousands of miles, a hundred beers, and one giant beard later and we are proud to introduce the ZERK 40. Co-designed with The Real Hiking Viking, a renowned thru-hiker with thousands of hiking miles under his belt, the ZERK 40 pack stands alone as the ideal combination of weight, durability, comfort, and accessibility.

Offer price: MSRP $220.00

  • Quality
  • Features
  • Fit
  • Durability


Overall this packet was comfy, roomy, and feature-rich, but still lightweight. That’s a combination that is hard to find, which will keep me reaching for this pack each time I want to do more with less.



  • Pockets for everything
  • Durable material
  • Perfect pack for long day outings


  • Needs hip pockets
  • Torso length is short
  • Hard to reach the side pockets while wearing the pack.

Are you an ultra-adventurer? Is your VO2 Max 55+? Have you ran so many 100 miles races you’ve lost count? Do you run all day on a single snickers? If that’s you, then you’re probably so tough you don’t even need a backpack!

For the rest of us, juggling work life, family life, social life, etc., can leave us with little time left over to do what we love. Time is all of our most precious commodity, and our ever-increasing busy lifestyles are leaving us with less and less of it to spare. Fortunately for us, the fast packing movement and new advanced gear like this is helping us all get some of it back.

As a full time traveling sales rep, part-time guide, kids in the near future, and in the middle of building a house, time isn’t something I have much excess of. Still the mountains are always calling and my adventure “to-do” list seems to only get longer. With most of the shorter weekend trips already ticked off over the last 15 years of adventuring, most of my remaining goals would typically take 3-5 days. Adopting the “in-a-day” fastpacking concept was a great way to still tackle those longer trips but in just a quickie weekend blitz. In order to do that, however, you gotta have the right gear, and a typical backpacking set up isn’t going to cut it.

When you need to go fast, a 60L backpack, with a sleeping pad bungee-corded to the top, a gallon zip-lock bag of trail mix in the lid, and a 1-liter Nalgene bottle clipped to your hip belt is gonna severely cut down the mileage you can do in a day. The Zerk 40, is not that.

Large front pockets allow for lots of space for snacks and water.


The pack is loaded with pockets and other features, but still, streamline and not cluttered like a lot of packs with similar features. That helped a lot earlier this fall when I carried this with me over a 32-mile, 14-hour push up three peaks in the Cascades. It was comfortable and carried well despite being loaded with gear and carrying it for 10’s of miles. The fabric seemed to be a lot more durable than must ultra-light gear, and it held up well against the rough granite we were scrambling through all day. All of the pockets make easy access to everything I needed throughout the day, and the still streamlined design prevented any snagging on branches as we moved over miles of off-trail bushwhacking. 

The roll-top closure and water-resistant fabric also kept my gear dry against the off and on rain we had throughout our trip. Ultimately, we did a lot of miles, a lot of elevation, and accomplished what we hoped for. The Zerk 40 enabled us to do it all quicker, and more comfortably, getting back to the car even with more energy and time leftover to attempt something else.


The torso was a bit short for me (5’ 10”), but I found the shoulder straps and the back panel to be very comfortable.


Clutter-free clean and simple look without sacrificing pockets and other features.


This pack is loaded with features. The large dual side-pockets are unique and were especially nice to have.


It’s neat and balanced, whether it is packed to the brim, or almost empty. Since the expandability and compressibility are done well, it doesn’t look like a yard sale when it’s completely full and doesn’t flop around when it’s nearly empty. That’s hard to do.


This is the category for which this pack was born for. It’s got every feature you could want and somehow does it while still being lightweight.


Many ultralight packs sacrifice durability for weight. The fabric on this pack strikes a good balance and is both lightweight and durable. Having no problem holding up to the abrasive cascade granite.

Room for Improvement

  • A more comfortable hip belt, perhaps with pockets, would be nice. Given that it’s 40L, it’s a bit large to be used as a vest pack so I can’t imagine ever removing the hip belt.
  • There should be two chest straps. When fully loaded with gear, the added stability would be an improvement.
  • There’s no upper attachment point for an ice axe so you’ll have to add your own.
  • I found it hard to reach the side pockets while wearing the pack.

The Final Word

Overall this packet was comfy, roomy, and feature rich, but still lightweight. That’s a combination that is hard to find, which will keep me reaching for this pack each time I want to do more with less.

Shop the Mountainsmith Zerk 40 on Outdoor Prolink. Not a member? Apply today!

About the Gear Tester

Outdoor Prolink Pro
Josh Stuart
Full Time Traveling Sales Rep -- Part-Time Guide :: Outer Element Adventures

Josh is an avid and relentless adventure who likes to do it all and spends every spare second outside. He’s been mountain climbing for 17 years, spent several years as a mountain rescue volunteer, and is an AMGA SPI and Apprentice Alpine Guide. When is he’s done working and not building his new home, you’ll find him climbing, hiking, running, surfing, paddle boarding, mountain biking, kayaking, or kite boarding. No matter what, he’ll be outside.

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