Exo Mtn Gear K4 Review

It’s been three years since my Exo Mountain Gear K3 pack review was published at Carryology. Recently, Exo Mtn Gear introduced a successor to this pack, the new K4. But instead of making a “better K3”, the Exo team started with a blank sheet of paper and a lot of heavy backpacking experience in the outback. So, they created an entirely new pack with a new frame and carry system. And even if the K4 is designed primarily as a mountain hunting pack, you can also use it for other backcountry activities. Especially if you want to carry more than 60 lbs of gear one day but still need the K4 to be your daypack on other days. I tested it for over 3 months in many scenarios, different terrains (mostly mountains), and various weather conditions – full summer sun, cold autumn rain, and everything in between.

By the way, be sure to check out additional resources available at www.exomtngear.com, especially their excellent podcast and recently started The Experience Project, which is an amazing resource for backcountry knowledge (not only hunting-related).

Design

Looks

Exo Mtn Gear packs are very different from your classic alpine backpacks. In a nutshell – they feature an external frame and carry system to which an actual bag is attached. The main reason is to carry an additional heavy load between the frame and a bag comfortably in the backcountry, over a long distance. A typical application for such a pack is mountain hunting in remote areas so that you can carry the game down to the camp or truck. But overall, external frame packs are known as the best and most comfortable heavy haulers in the backpack world. For anything above 60 lbs, this system is superior to any internal frame pack in terms of comfort, and a slight weight penalty is fully acceptable here. They are also scalable and adaptable to a variety of outdoor scenarios. Each size of the K4’s main bags can be considerably compressed, so you could use even the biggest one in a day bag mode on the K4 frame.

The full Exo Mtn Gear K4 system I used for the last couple of months:

• K4 frame with 3600 cu-in medium-sized bag for general use and that includes a lid of almost 650 cu-in additional volume.
• the above extended even more with a dedicated 3600 cu-in drybag carried between the frame and main bag
• a small 2200 cu-in daypack as an optional day-hiking bag.

With these components, I could scale my carry system from a maximum of 7850 cu-in capacity as a base camp hauling set down to 2200 cu-in as a daypack mode. And anything in between, as the lid can be attached to all K4 bags, even the small one. Of course, if needed, bigger options are available from Exo, up to 7200 cu-in in a main bag. Still, they are more cold-season-oriented options for real expeditions, where you need more volume for warm puffy jackets and pants, low-temp-rated synthetic sleeping bags for drying clothing out during sleep, etc. Whereas what I was carrying was mainly summer or early fall clothes with some optional insulating layers (must-have in the mountains), rain gear, water, food, camping stuff, some gear for my wife and son, and quite a lot of photography equipment (as usual much more than I used, but that’s a classic photographer’s syndrome). So when fully loaded and extended to 7850 cu-in with water, a tripod, trekking poles, and other gear strapped outside, my pack crossed the 80 lbs mark on a luggage scale. That was heavy! But I wanted it heavy for testing purposes on that trip; otherwise, what would I tell you?

Construction, Materials, and Hardware

The foundation of the K4’s frame is a system of two vertical stays and horizontal links made of dense carbon fiber, connected by sewn-together Cordura parts, which make the frame one rigid piece. In the K3 pack, the titanium welded pipes formed the frame, which was light and rigid, but also stiff. The new frame adds flexibility to the carry equation, so the pack follows all torso movements for less restricted motion and comfort. Other parts of the carry system are made of Cordura, too, with very detailed selection of supportive padding foams. That is especially true for the oversized lumbar pad, as finding this foam was the biggest challenge, according to the Exo Mtn Gear founder. After all, the K4 must support even a load of 100 lbs (or more) safely and comfortably. The Exo team tested every piece of material, hardware (some custom-made for Exo), and even the sewing thread before using it on this pack. All packs are sewn precisely at the Exo Mtn Gear facility in Boise, ID. And yes, the K4 is a true all-in US-made pack, where both the frame and the bag are produced in the US, using US-sourced and made components. It’s also an extremely robust construction – I know because I didn’t baby my K4. I pulled all straps to the maximum, pushed the zippers’ integrity beyond typical use, and scraped the fabric against a sharp rock. After all this, my K4 pack is still in perfect condition, without any damage – just a bit dirty here and there.

Features

As I mentioned before, the flagship feature of the K4 is the ability to put an additional heavy load between the pack and frame. But some other features of this pack include:

• elastic open side pockets with optional pass-through channels for side compression straps and additional small pockets with angled openings
• long side zipper pockets
• angled compression straps prevent the pack from sagging down with cargo between the frame and pack
• the front and bottom compression straps cleverly compress even the biggest 7200 bag to a tiny daypack mode. It’s a great way to bring just one pack for multiple uses.
• PALS panels on the shoulder straps and waist belt for easy attachment of small pouches, knives, or other items that are MOLLE-compatible
• angled PALS between the belt and pack for a dedicated 32oz Nalgene (or similar) bottle carry insulated pouch (brilliant!)

Performance

Space and Access

The K4 as a pack system is as scalable and adjustable as you can dream of. There are 4 different bag sizes – each bag is distinct in design as they serve slightly different purposes: 2200 daypack, 3600 extended weekender bag (or a lightweight week bag), 5000 all-year weekly bag, and 7200 one for long expeditions – anywhere, anytime. Add to this a removable lid, and the K4 system allows for any volume starting from 2200 cu-in and up to almost 8k cu-in… plus that frame-cargo space. All bags except the smallest one share a roll-top top-loader design, and all have additional side or front openings for easy loading and quick access to any part of the bag. All pockets can be quickly accessed too and all zippers are glove-friendly. The 2200 cu-in pack is a panel loader style with an integrated lid pocket – a very convenient solution on a daypack. Overall, it’s evident that the K4 system was designed for and by avid outdoors people.

Pockets and Organizing

Depending on bag size, the organizing can vary. Still, as a principle, you get one substantial central cavity, a dedicated hydration bladder compartment, two long side zipper pockets, and two side open pockets. The hydration pocket has a waterproof lining, so the pack’s interior will not get wet in case of a bladder leak. The 2200 daypack has a slightly different configuration with an additional top pocket and inside “hidden” zipper, as it’s by default a bag to be carried without the additional lid. However, with the optional strap extenders, you can use the K4 lid also on the smallest bag. Long side pockets are great for a spotting scope, tripod, or other heavy and long objects you’d like to protect from the elements. Side “bottle pockets” can be used with compression straps going crosswise inside, leaving the pocket open for storing bottles, a cooking system, or a rolled jacket. Or with compression straps over them to tighten down long objects that are partly kept inside (like a tripod). There’s even a tiny flat extra pocket there with an opening accessible with a pack on the back, which is great for snacks or for clipping a pocket knife inside. My 3600 cu-in bag also had a stretch front pocket, which I used mainly for quick-access items like my rain jacket (folded flat). And you have the lid – a removable, spacious, double compartment. It’s a classic design with no frills and no gimmicks, and it stays perfectly in place when cinched down with front and back straps.

The K4 has PALS slots on the straps and waistband. I avoid adding bulky pouches to my waist belt as they often interfere with natural arm movement, but a slim pocket on a belt is always welcome. The dedicated K4 Hipbelt Pouch holds my EDC kit ready and close at hand. I also usually carry a small fixed blade on my shoulder strap, and with the K4’s attachments it was comfy and easy.

But the real hidden treasure is the way the Exo guys attached the Nalgene bottle holder – at about a 30-degree angle, located between the waist belt and the bag. It never gets in your arms’ way and is naturally easy to access with the pack on your shoulders. Why did no one think of such a water bottle placement before? It’s brilliant!

And finally – using the cargo space. To use it, unbuckle the side compression straps, release the lid held by the top hooks, and open the cargo area between the frame and bag. Now, you can place the load, tighten it to the frame firmly with dedicated straps, and re-attach the bag. Buckle up all straps, attach the lid, and you’re ready. The whole process is considerably easier and faster than it was on the K3. The angled compression straps prevent the bag from sagging, so a pack with cargo sits balanced on the back. If the object you need to carry is wider at the bottom, you can also lose the bottom compression strap and create a cargo shelf. But in most cases, it’s still better to carry the additional load high, wedged in a V-shaped space between frame and bag.

Comfort

The frame and support are the most critical aspects of a heavy hauling pack. Not the weight, not the bag design, but the frame and carry system are everything if you put 80-100 lbs on your back. The base weight of the K4 3600 (frame, pack, lid) is just 5 lbs 8 oz, and it is remarkably lightweight for an external frame pack of this comfort. It’s even lighter than many classic internal frame packs of this size! In a base camp hauler or a cargo-carry pack, a couple of ounces more or less do not matter – but comfort and strength do, oh yeah! Big external frame packs are entirely different animals than ultralight packs, which seldom carry more than 40 lbs.

The K4’s entirely new carbon frame transfers hefty load via an upgraded carry system and distributes that weight to the hips and torso of the carrier. But that frame still has some flex, so it follows all the body movements. The shoulder straps and an enormous waist belt are well padded with special foam, which the Exo guys selected after months of testing of various types. The lumbar pad is sized to support a heavy pack, but the foam inside is not the same as in the pack’s shoulder straps. It’s also very different from what other brands use in classic packs. The standard foam would instantly compress to almost zero cushioning under a fully loaded 7200 cu-in pack plus 60+ lbs of cargo load. But that special K4’s lumbar pad works great, and together with the waist belt, they transfer most of the weight to the hips. That is more comfortable and safer for the backbone than putting excessive weight on the shoulders. Undoubtedly, it’s the most comfortable heavy hauler I’ve ever had on my back!

To ensure maximum comfort, you first need to measure your body and order a specific size of frame and belt, then micro-adjust it to your body shape. It’s easy and intuitive, but you can still check Exo Mtn Gear’s excellent video guides to ensure a perfect fit. The back panel and straps give some ventilation and keep sweat away thanks to heavy-duty mesh. But if you think you won’t sweat when carrying 80 lbs for a couple of hours in the mountains – you are wrong. No pack would help you in this regard – the brutal truth is, the only help can be your stamina and training throughout the year, well before hiking season starts.

The K4 remains very comfortable in a daypack mode but is still heavier than most dedicated daypacks. Even with the smallest 2200 bag, the system at 4lbs 9oz is not lightweight by today’s standards of alpine packs. However, the K4’s primary role (as a pack made with mountain hunters in mind) is to bring that weighty game back to the base camp at the end of the day. But it would also work great as a recon pack for the backcountry or as a platform to carry a heavy and bulky load one way to the camp (to be used later in a daypack configuration). I hiked and even scrambled quite a lot with the dedicated 2200 cu-in panel-loader bag or a compressed 3600 one (after utilizing its total capacity as a base camp pack). It worked fine, but a full-size frame is still more optimized for backcountry hiking than climbing or scrambling. So, for pure non-hunting use on technical routes, via-ferratas, or for moving in rocky vertical terrain, I’d instead use a lightweight and agile dedicated climbing pack, which I could still carry comfortably between the K4 bag and frame on approach to the base camp or mountain shelter.

Weatherability

It’s a seriously weatherproof pack, and I tried it the hard way! The main fabric is waterproof, so it’ll be fine in light rain or snow. But still, some water can leak to the inside through stitching lines, especially during a long-lasting downpour. If this is your primary concern, use either an aftermarket rain cover or (better) get a dedicated waterproof drybag insert for your pack. Exo offers them for all bag sizes except the 2200 daypack. Additionally, you can Velcro these bags inside for perfect fit and operational convenience. Only a sealed drybag like this provides total waterproofness – so if you expect super rainy weather or when crossing rivers and waterfalls, there’s no better option for you. Of course, the lid or side pockets are still unprotected, and side access to the bag is impossible – but that’s a compromise I accept. Still, it’s the best solution to protect your main gear from water. As a side note – remember that a fully sealed pack can sometimes be more of a nuisance than a benefit. Especially on more extended expeditions, it can prevent moist clothing from breathing and drying out, which can quickly start gross issues like odor or mold buildup inside a pack.

Alternatives to Consider

Hill People Gear – Decker Pack Frame

Stone Glacier Sky series

Mystery Ranch Metcalf series

Kifaru ARK Frame system

The Good

This pack is lightweight for what you can carry with it, super scalable and adjustable, and not overly complicated to adjust and use. It’s incredibly comfortable with a heavy load, and the manufacturer offers excellent service and warranty. The K4 system is tough as nails. It was designed by avid outdoorsmen who test and try everything they make. It has useful, unique, thought-out features and clever accessories. And it’s all made in the USA.

Not So Good

This is not the best option if you’re on a tight budget ($675 for the base K4 3600 system: frame, bag, and lid). It’s also not lightweight and nimble when used as a mountaineering daypack.

Verdict

If you’re looking for a heavy-duty and tough-as-nails base camp-style pack to carry a lot of gear, the Exo Mountain Gear K4 should be on your shortlist. And if you’re also a mountain hunter, the K4 should be on top of it. It’s a very sturdy pack, crazy comfortable, and can play many roles thanks to its scalability and modularity. The K4 would be great for leading backcountry expeditions and hunts. It’s a fantastic option for bushcraft instructors, expedition photographers, etc. And if you want to use it as a daypack after getting to your base camp with all your gear, you can just use the compressed 3600 (or bigger) bag on the K4 frame or a dedicated 2200 panel loader bag. I plan to use my Exo K4 primarily as a base camp hauler, as it can handle weighty loads comfortably, which an internal frame pack can’t offer. Still, remember that the Exo Mtn Gear K4 is a specialized product, and it’s not a universal solution for everyone.