Zerk 40

$219.95 has 92% five-star reviews on Trustpilot.


Co-designed with The Real Hiking Viking (a renowned thru-hiker), the Zerk 40 Backpack is the product of countless hours, miles and beers. After selling out during its debut, the Zerk won the Backpacker's 2020 Editor's Choice Award.

While spending thousands of miles on trails using a wide variety of products, The Real Hiking Viking had plenty of time to dream up his ideal thru-hike backpack. After teaming up with Mountainsmith, this dream became a reality. Designed for thru-hikers doing some serious miles, the Zerk cuts down on weight while still providing an abundance of features.

Meet the Zerk - a feature-rich pack with a minimalist mindset. Built to keep you propelled up the trail, every single feature was designed with the lightweight thru-hiker in mind.

Wide Mouth Roll-Top Access: easily pack your bag as the rolltop gets wider as it opens. Perfect for stashing additional gear, easily secure it in one of two ways: clipping the ends together or securing them down the side.

Wide Shoulder Straps: designed to keep you comfortable on the trail, the ultra-running inspired straps keep your pack’s weight evenly distributed across your torso.

Dual Mesh Shoulder Pockets: designed to keep you trekking on, the pockets stash anything from bottles to snacks and maps to your GPS. With two pockets, one large closing pocket and one small stash pocket on each shoulder, the possibilities are endless.

Stiff Atilon Foam & Breathable Mesh Back Panel: the lightweight structure of the Zerk not only keeps the weight down but keeps your back cool, allowing it to breathe.

XXL Side Pockets: perfect for stuffing those ‘can-I-fit-this?’ items. Waterbottles, your map, a rain jacket, easily reach the pockets with the pack still on your back.

Outer Mesh Pocket: ideal for stashing snacks and trash, easily reach these pockets with the pack on your back.

Secure Overtop Webbing Compression Strap: built to keep your gear secure and snug, the compression straps also provide additional attachment points.

Low Profile Side Compression Straps: secure your gear down for an even load and store additional gear on the outside (like your tent poles or umbrella).

Massive Stretch Mesh Front Pocket: keep your rainjacket and other essentials easily accessible.

Removable Bear & Gear Canister Straps: for everything you can’t fit in the pack, easily strap it down with multiple attachment points to customize your gear storage locations.

Reflective & Removable Bungee Cord: perfect for strapping down an extra layer, easily remove the excess weight when you don’t need it.

1.5" Removable Waist Belt: easily shed those ounces without ruining your pack. For those light trips where you don’t need the extra support, simply unbuckle the belt and save it for another day.

Hydration Hook and Hole: Hang your bladder securely inside and loop the straw to attach to either one of your shoulders.

Ice-Pick Loop: Keep your gear safe and your pick easily accessible by hanging it on the ice-pick loop.

Materials: 100d Nylon HT w/ 200d Spectra Double R/S TPU, Atilon Foam (Backpanel), 210g Stretch Mesh, EVA & PE Foam

Dimensions: 18.5" x 11.75" x 5.75" / 47 x 30 x 14.6 cm (H x W x D)

Volume: 32L (compressed) 40L (at capacity)

Capacity: 30lbs

Weight: Packed Weight - 28oz // Trail Weight (Straps detached) - 25oz

Shipping Information offers free ground shipping anywhere in the continental US for any order of $49 or more. orders under $49 ship anywhere within the continental US for a flat rate of $4.95.
​Shipment tracking typically takes 1 - 3 business days to update. You will receive an automated shipment notification email as soon as your tracking number becomes available. If you do not receive your shipment tracking email within 1 - 3 business days be sure to check your spam or junk mail folders. Standard shipping takes approximately 3 - 7 business days from the time the item ships. During the Holidays the estimated shipping window is extended to 7 - 16 business days. We appreciate your understanding and patience!

​Unfortunately we're unable to promise or guarantee delivery by a specific date and don't offer overnight or express shipping at this time. We also do not currently ship to Alaska, Hawaii, APO/FPO addresses, US territories, or international addresses. Please feel free to reach out to with any questions!


Potential Shipping Delays: The unfortunate situation affecting countries worldwide has greatly impacted all of our lives. We understand that this is a difficult time and we want you to know that the family is working hard to provide you with exceptional customer service and awesome gear. Due to increased order volume, mail carrier delays and the additional recommended safety measures we are taking to protect our teams, it may take longer than the usual 5 -7 business days for your order to be delivered. Many orders are shipping within the estimated 5 - 7 business day window, while others can take up to 7 - 21 business days to be delivered depending on warehouse location as each US State has a unique method of dealing with this serious situation. 
We are doing our best to process and deliver your order as soon as possible while keeping employees safe. Please keep an eye on your email for all order and tracking updates. We'll email you once your order ships. We appreciate your patience and understanding during these unique times. As always, if you have any questions, please reach out to and we'll do our best to assist you!

100% Guaranteed Returns

We understand that not every purchase works out, which is why we offer a 100% satisfaction guarantee. New, unused gear in original packaging and hangtags can be returned at any time within 30 days of purchase for a refund to your original method of payment. If the original method of payment is unavailable, we will issue your refund in the form of store credit.

How to return by mail

Due to high demand, our returns process may take longer than usual. Typically, we will issue a refund within 10 business days after we receive your package. It may take up to 3 additional weeks for your bank to refund your credit card or for a refund check to arrive. Thank you for your patience as we process returns as quickly and safely as possible. Please contact for all return requests.

Follow these three steps:

  1. Print your shipping label
    Reach out to us a and we will email you your label. To make shipping a return even easier, we offer a prepaid return shipping label for eligible U.S. customers returning products that don’t need to ship freight. Some exceptions apply. Reach out to to initiate your return request, and to ensure the item is being returned to the correct warehouse/address.
    Please note: $8.95 will be deducted from your refund to cover return shipping for standard size/weight packages when you use the prepaid shipping label provided by This charge only applies if your return is mailed using a prepaid label our team provides, but will not be deducted if you pay for the return shipping yourself. Shipping costs to return oversized items (such as coolers, skis, furniture, large stoves and tents, etc) will be calculated on a case-by-case basis. Please don’t hesitate to ask if you have any questions about typical return shipping for an oversized item you may order.  
  2. Pack your return
    Pack your item(s) securely and include the original product packaging and tags. 
  3. Prepare & ship your package
    Tape your package securely and affix your return shipping label to the outside. (Hint: If you cover or remove all existing shipping labels, you can usually reuse the bag or box your order came in.) Drop off your package at a carrier location near you. We’ll email you once we’ve issued a store credit or a refund – typically within 10 business days after we receive your package. It may take up to 3 additional weeks for your bank to refund your credit card. PLEASE NOTE: PREPAID LABELS EXPIRE 15 DAYS FROM DATE WE SEND THEM TO YOU.

To note:

  • If we have questions about your return, we will contact you by phone or email. 
  • Returned merchandise that does not meet the conditions of the Return Policy will be declined and a refund will not be issued. 
  • All sales are final on gift cards, lift tickets, and passes, as noted at time of purchase.
  • If you prefer to work directly with a carrier to ship your return, please reach out to to request an RMA and return shipping address.

Mail-in return exceptions

Some items cannot be returned via our return portal, including the following:

  1. Hazardous materials
  2. Food items
  3. Oversize items
  4. Some Corporate & Group Sales items

Mail-in return exceptions may apply to coolers, tents, kayaks, surfboards, SUP boards, cargo boxes, car racks, indoor cycles, power stations and more. 

Store Credits

Store credits issued for returned products will expire one year from the date of issuance. 

All other store credits expire 90 days from issuance, including credits issued by our Customer Success team or as part of a promotion.

Manufacturing Defect/Warranty Claims ​

If you experience a manufacturing defect, or it's outside of’s 30 day return window, please contact the manufacturer directly. does not provide any direct warranty services, though your purchase may be covered by a brand or manufacturer warranty. If a warranty claim requires a Proof of Purchase from, please contact and we'll be happy to email a copy if needed.

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