The Osprey Mutant 52 is categorized as a “climbing/mountaineering” backpack, which is a bit unclear, since there’s a big difference between packs that are worn while climbing versus packs that are used to carry gear to a climb. The Mutant 52 is more the latter. After trying this pack in a variety of contexts, I think it’s best used for mountaineering, multiday ski touring, backcountry rock climbing, and possibly alpinism (i.e. multiday snow, ice/mixed climbing). It’s also superb for packrafting!
I tested the Mutant on an overnight ski tour, as a cragging pack in the frontcountry, and on a three-week packraft expedition in the Amazon rainforest. I’ve been very pleased with its functionality, adaptability, and durability across a broad range of environments and uses. I’d say this pack as an excellent all-rounder: not a specialist at any given use-case, but a “quiver-of-one” that spans many uses.
The basic architecture of this backpack is familiar to the realm of mountain-approach packs–i.e. something you would carry for a three-day rock climbing trip in the Sierra or the Wind River Range. It has external straps that allow it to function brilliantly in a mountaineering or ski-mountaineering context. In terms of general functionality, it has everything you would expect from a modern, light pack of this sort: comfortable hip and shoulder straps, a “floating” top lid that can be used to compress bulky items on top of the pack, and a speed-lid drawstring on the main compartment than can be easily opened and shut with one hand.
I find 52 liters to be the ideal size for two- to four-day trips when packing thoughtfully, or an oversized daypack for trad climbing in colder months when I want to shove in a rack, puffy jacket, thermos, lunch bag, etc., without any fuss. The pack is designed to comfortably carry up to 50 pounds. In the rainforest, I found that it’s really most comfortable up to about 45 pounds. At 50 pounds and beyond, the load started to sag uncomfortably onto my shoulders.
Weight, materials and strip-ability
This pack weighs 3.4 pounds (3.2 lbs. for the 50-liter S/M size), which is about average for packs of this size and general-use type. The Mutant has durable 420-denier pack cloth on the base and high-wear areas, and lighter 210 denier nylon for the rest of the pack body. The extra features on the Mutant make it a little heavier than the lighter packs in this class, but the two-fabric design helps keep the weight down.
In terms of weight, the Mutant sits between two comparable Black Diamond packs: the Mission 55-L ($230) is constructed of 420-denier nylon and weighs 3.88 pounds, while BD’s lighter Speed 55-L pack ($190) weighs 2.75 pounds and is made of the same two-fabric design, but has a simpler lid and fewer straps.
The Mutant pack can be stripped down nicely, an attribute that improves its utility for climbing and backcountry missions. You can remove the top lid, helmet carry, hip belt, plastic frame sheet, and the pair of aluminum stays, reducing the pack’s weight to 1.8 pounds, which is a light pack indeed. The pack includes a small cover that stows in a hidden pocket and secures over the drawstring opening when used without a lid; it keeps rain and pine-needles out of the pack.
Simple additions give this pack a functionality for mountaineering and ski activities. Two ice-tool attachments hold mountaineering axes or water-ice tools nicely, and gear loops on the hip straps are useful on technical mountain routes. In addition to side compression straps, this pack has reinforced ski-carry straps and shallow wand pockets. While these reinforced straps are not necessary for an A-frame ski-carry, they make for a more stable ski-carry over long distances, and are durable enough to not get worn out if this is how you typically use the pack. The wand pockets, while adding minimal weight, greatly increase the security of carrying wands, pickets or other tubular items on the outside of the pack. I found they also fit the ends of break-apart kayak paddles, a nice benefit for packrafting expeditions.
Snowshoes can be strapped to the sides, but it can be a fussy task because the lower compression strap does not unbuckle (it just has a slide-buckle). More on this later. The Mutant does not have a crampon pouch, but the daisy-chain connections on the front can be used to strap crampons with cord or elastic cord. I wish Osprey had added some burly elastic cord for this purpose, as it seems like an obvious thing to include.
This pack is ideal for overnight backcountry ski missions–you can hike in with the lid atop the pack for extra capacity, then use the pack body alone on the mission. It works great as a ski pack, with a caveat being the lack of cord for strapping crampons.
Backcountry rock climbing
A “mountain approach” pack for climbing in the backcountry really just needs to be a good backpacking pack that also holds a rope well. The Mutant is great for backpacking; the simple, spacious main compartment is complemented by a really large lid that has two pockets. I find this useful for organization, I keep small items like my knife, GPS and sunscreen in the small, topmost pocket, and the second, larger pocket can hold a camera, water bottle, maps, etc. It will fit most folded maps, which is nice. There is also a pocket for a hydration bladder.
One caveat with the lid: if you want to use the included “helmet carry” pouch atop the lid, it connects to two toggles inside the upper lid pocket; thus you cannot stow items in the pocket if you want to use the helmet pouch. This is basically a waste of a pocket–the pouch doesn’t need its own pocket. Osprey indicates that the pouch can secure to the front of the pack, but that option isn’t available if that space is taken by crampons. My solution was to tie the pouch onto the daisy chain atop the lid so I could use the pocket.
The Mutant has a standard rope-carrying strap (atop the main compartment, beneath the lid) and the upper side compression straps can be unbuckled to secure a rope–but only high on the pack. My main gripe with this backpack is that the lower compression straps cannot be unbuckled. Rope coils swinging around is tolerable on a 10-minute hike to a sport crag, but becomes annoying on a 10-mile approach into the Sierra; I always strap those rope coils down to keep them from swaying around. Long rope coils can be painstakingly shoved beneath the lower straps on the Mutant, but it would be so much easier to secure them if the buckle could be undone–I’ll likely modify mine.
In the backcountry you can strip this pack down to a “mission pack” for scrambles and easy climbing, but it’s still much larger than anything I’d carry for a serious rock climb. Ideally you’re never rock climbing with a load that large. It could definitely be a good pack for alpine missions where you need to carry sleeping bag, tent, stove etc., especially if you also need to carry pickets and wands. If you strip the lid off, the pack will not impede your head while looking up–a necessity for climbing. I probably wouldn’t climb water ice near my limit while wearing this pack, but it would carry just fine on moderate ice and mixed climbing on larger routes where a large pack could be useful. You could use the attached gear loops on the hip straps for easy climbing, but you’ll have more access to your harness gear loops if you strip the hip belt off. As with the Mutant 22, there is also a “three-point haul system” that allows the pack to be tied to the end of a rope and hauled up the pitch.
The Mutant 52 has a couple more caveats when it comes to alpine climbing. The four-season design of this pack is not as durable as alpine-specific packs. Also, there is still some built-in bulk (suspension system, hydration pouch, etc.) that you will not find in rigorously minimalist alpine climbing pack designs. For example, the stripped-down Mutant with a hip belt weighs about the same as Hyperlite Mountain Gear’s 2400 Ice Pack ($310), however the latter is much more durable and designed specifically for technical alpinism. That said, I’d prefer the Mutant for summer backpacking.
This pack also works really well for the growing niche sport of packrafting. The daisy chains on the pack allow a packraft to be lashed on, and the wand pockets secure parts of breakdown paddles that are strapped to the sides. The pack has a drain hole, which is useful after getting soaked in rapids (I just line it with a heavy-duty trash bag), and the generously large pockets in the lid allow water bottles, sunscreen, food, etc. to be easily accessible while the pack is lashed to your raft. The Mutant was great for my rainforest river expedition.
Overall the Mutant backpack is an excellent generalist–you can use it during all four seasons on activities ranging from summer backpacking to winter mountaineering. Its size is perfect for multiday, lightweight winter trips, with or without skis, as well as summer trips loaded with climbing gear.
Generalist gear often suffers from being too heavy, but the Mutant’s modular construction lets you do away with excess weight for a “mission-style” pack that’s highly functional. There are a couple finer points that I would change–such as adding crampon cord, a more independent helmet pouch and releasable side buckles–but the overall design is solid. I’d use this pack for just about any venture that requires a pack larger than 35 liters during any season of the year.
Drew Thayer has been climbing for 15 years, including 10 years of ice climbing and nine years of alpine and big-wall experience in the U.S., Peru, Argentina, Canada and Alaska. He received a Copp-Dash Award in 2016 for an expedition to Alaska, where his team packrafted back to civilization after establishing four new routes in the Neacola Mountains of the Aleutian Range.
Excellent all-around use, from summer backpacking to ski mountaineering
Comfortable and relatively lightweight (3.4 lbs.)
Strips down well if you only want to carry bare essentials
Carries skis really well
Large capacity lid is really useful
Need to improvise your own system to strap crampons to the outside
The top pocket is rendered useless if you secure the helmet pouch on top instead of the front
Hard to secure ends of rope coils with non-detachable lower side buckles
Overall design isn’t tailored specifically to alpine climbing as well as other backpacks