The Exo Mountain Gear K4 is the culmination of over ten years of experience in the backpack industry. It was designed and tested over three years, and the results are impressive. I’ve been fortunate to use and test many great packs over the years, so I’m excited to tell you what I like and don’t like about the K4. If you’re familiar with Exo packs, you’ll notice that K4 differs from previous versions. Continue reading to see what’s new.

Exo Mountain Gear K4 Backpack

The K4 is currently available in three bag sizes from 3600 to 7200 C.I., with more options on the way. K4 is offered in four frame heights from 22″ to 26.5″. And there are five hip belt sizes to fit just about anyone.

Color options include Coyote Tan, Ranger Green, and First Lite Fusion. A new line of accessories, including my favorite, a water bottle holder, is available.

The bags still detach easily from the frame for quick access to the load shelf, although the attachment point at the top differs. Speaking of differences, the frame is totally different from previous Exo packs.

New top attachment system is shown with Ranger Green K4 and Coyote Tan Prototype bag for clarity.

Click here for more details or to see the latest updates on K4.

My Test Packs

I was given a prototype K4 7200 with a 25″ frame to test last fall. Most of my experience is with that pack. This winter, I also received production versions of K4 3600 with a 25″ frame and K4 7200 with a 26.5″ frame. All have small hip belts. I’m 5’10”, weigh 190 lbs, and have a fairly athletic build. Both frame sizes were comfortable for carrying light to heavy loads. The 26.5″ frame carries the heavy loads slightly better for me and is my preferred frame height. All three packs included a lid, water bottle pocket, and hip belt pouch.

K3 (left) next to the new K4 (right).
K4 Frame

K4 uses two vertical composite stays instead of the formed titanium frame Exo has used in prior packs. (see photo above) Three horizontal stiffeners allow the frame to flex with your movements while keeping the frame from barreling. Six shoulder strap attachment points allow plenty of adjustment for most torsos. There are four horizontal compression straps attached to the frame. Two secure loads to the load shelf, and two attach the bag to the frame. If using only the frame, you can use all four straps to secure a load since the buckles are all opposing on K4.

K4 Comfort

The previous Exo frames have worked well for me, as I discussed in my reviews of K2 and K3. The Exo Mountain Gear K4 was even more comfortable. It feels like it locks onto my hips and doesn’t move, even with heavy loads.

A plastic sheet makes up the hip belt’s backbone, transferring weight around the hips and reducing pressure points. It also supports the water bottle pocket and, soon, a rifle carrier. The shoulder straps are comfortable and spread the weight across my shoulders. The K4 frame has been absolutely stellar, whether packing light or heavy loads.

K4 Pack Bags

At launch, the K4 is offered in three sizes. The 3600 and 7200 feature a single zipper along the side of the back panel to access the main bag. The K4 5000 brings back the horseshoe access to the main bag.

All bags also have a roll-top opening and zippered side pockets for spotting scopes and other items you want quick access to. I prefer a top opening for the side pockets, but I’m in the minority, and Exo went with the most popular configuration among testers: the vertical zippers.

The side pockets are the same size regardless of which bag you choose. I had no issues fitting my 80mm angled spotting scope.

The stretch pocket on the back of the pack is a great place to quickly stuff a rain jacket, gloves, or other items. A water bladder pocket is located between the main bag and the frame and has a zipper at the top for easy access. I like that it’s separate from the main bag.

Two additional stretch pockets on each side of the bag are great for items you want to access without affecting or opening the main bag. The stretch pockets can be pretty tight if you have the main bag full and also the zippered side pockets.

K4 Lid

The K4 lid is a “floating lid” that works well for securing loose items to the top of the pack. I prefer this lid type for attaching heads and/or antlers on successful hunts. It can also be removed anytime you don’t need the organization or extra capacity. The lid fits perfectly over the top of the main bag, providing extra protection from weather and debris. There is a small pocket on the top for small items and a larger main pocket.

I also added a Stash Pocket inside the lid for even more organization. I like the size of the lid as I feel it’s big enough to carry the things I need but not huge and floppy.

A Note From Dioni Amuchastegui

Doini is long time Rokslide member and hard-core backcountry hunter. He was also one of the many testers Exo recruited for the K4. I asked him for his thoughts; here’s what he had to say.

“Over the last two seasons, I’ve used what would become the Exo Mountain Gear K4. Exo’s only requirement of me was to use the packs hard and be honest about what I didn’t like so that it could be improved. 

In that time, the number of changes, tweaks, and refinements stand out nearly as much as any individual feature. It seemed like every time I stopped by the shop, they were changing parts on my pack, checking for wear spots, or giving me different components to try out. All this is to say that the level of refinement and thoughtfulness that made this a comfortable, durable system is hard to comprehend. 

At this point, I’ve spent well over a month wearing it, covered hundreds of miles, and carried out some of the heaviest loads I’ve ever packed. Where the K4 ended up is easily the most comfortable pack I’ve ever used”.

K4 Accessories

Most accessories attach using laser-cut MOLLE panels on the frame and hip belt. My favorite new accessory is the water bottle holder. The attachment and location are the best I’ve used.

The zippered belt pouch attaches securely and opens and closes easily with one hand. The K3 stash pockets work the same as before with the K4. I like them because they are lightweight, quickly removable, and organize small items.

Other accessories, such as an InReach Mini holster, a crib panel, and dry bags, will be coming soon. The new laser-cut MOLLE panels also work with MOLLE accessories from other companies.


To date, I have used the K4 for one season. It held up very well, and I don’t expect the pack to have any problems as I continue to use it. Durability was one area the Exo crew focused on during K4 development. They made many little improvements to ensure K4 would last as long as possible. Read more on that here.


The Exo Mountain Gear K4 is the most comfortable pack I have tested. That’s really saying something since I’ve used packs from what I consider the top three backpack makers in the industry.

The bag design is streamlined but includes many great features hunters will appreciate. Some of my favorites are the simplicity of the bag-to-frame connections (which make the load shelf easy to use), the water bottle holder, and the integrated laser cut molle for attaching pockets and accessories. I recommend the Exo K4 to anyone looking for a comfortable, well-thought-out pack system for backcountry adventures. Click here to order.

Comment or ask Justin questions here.

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Justin Crossley
Justin Crossley is married to wife Breana and they have two kids; Alissa and Dylan. Born and raised in Western Washington he grew up fishing anything that would bite, and hunting black tail deer using rifle and muzzle loader with his dad and brother. Some of his fondest memories are those where he explored the wilderness and learned about hunting and fishing. As he got older his passion for the outdoors grew and he started hunting everything from upland birds, to predators, to any big game animal he could get a tag for. He has had the privilege to have friends and family who enjoyed the outdoors like he does and has made priceless memories with them on many trips. Justin’s kids have both been raised around hunting and fishing, and son Dylan recently killed his first deer at age ten. Justin enjoys every type of hunting and will hunt archery, rifle, or muzzleloader to extend his hunting season as much as possible. His favorite hunts take place in the backcountry with camp on his back. He has learned to hone his craft in long range shooting, archery, and reloading. He always strives to learn more and improve himself as a hunter. Justin has always had a passion for helping others expand their knowledge and love of the outdoors.