Osprey Mutant Nimsdai 90 Review

© UKC Gear

An expedition pack primarily designed for mountaineering in big overseas environments, the Mutant Nimsdai 90 aims to offer great load-carrying abilities to get you to the peak, and a streamlined and stable feel for climbing. Developed with input from brand ambassador Nimsdai Purja, it is clearly built for demanding and kit-hungry objectives up high. Whilst the UK can't offer any alpine or greater range style adventures, there are still some great multi-day mountaineering and backpacking objectives to be had here. We've used this large-capacity pack on a number of overnight Scottish trips, something for which it has proved well suited. 

The Mutant Nimsdai 90 providing comfortable load carrying for multi-day Scottish Winter mountaineering  © UKC Gear
The Mutant Nimsdai 90 providing comfortable load carrying for multi-day Scottish Winter mountaineering
Pros: Supportive with a heavy load, stable when climbing, durable to take the knocks, and big enough for expedition use
Cons: Perhaps a bit basic if you're mostly walking rather than climbing; not as comfy as most trekking packs over a long day

Size and Capacity

At a whopping 90 litres, this is a big expedition-worthy pack, and in the UK it's more geared towards overnight winter mountaineering and multi-day summer backpacking and climbing objectives. On an overnight mountaineering trip to Ben Alder this winter, I was glad to have this pack with me. With tent, sleeping bag, food and cooking equipment, a climbing rack, and a bulky camera all packed in together with enough warm layers for a particularly cold night, I was still left with a bit of wiggle room and some external carrying features I hadn't needed to take advantage of. On a longer or more expedition-style trip, you'd be glad to have this extra space available.

The large capacity provides enough room for multi-day Scottish Winter mountaineering  © UKC Gear
The large capacity provides enough room for multi-day Scottish Winter mountaineering

Weight and Durability

Large packs tend not to come light as they often require sturdy materials and heavier design aspects to balance comfort and durability with the load carrying capabilities you need with a larger volume of gear. At 2.1kg the Mutant Nimsdai 90 is however pretty reasonable for a pack of this size, and if you want to reduce that it can be stripped down a bit with removable features (back panel, lid etc) for climbing or a summit push.

Tought durable 210D ripstop fabric makes up the main body of the pack  © UKC Gear
Tought durable 210D ripstop fabric makes up the main body of the pack

The pack uses some tough materials which have been selected for their good weight to durability. The main body contains a 210D Nylon ripstop fabric able to take a beating that you'd expect from mountaineering. On the bottom you get a 600D high tenacity nylon which is great for this area that sees a particularly high amount of wear.

Environmental factors have also been considered by Osprey when selecting these materials, with the use of recycled nylons, which are PFAS-free and bluesign approved.

Back System and Carrying Comfort

The back length is fixed on this pack, so it comes in two different sizes: S/M (35.5cm-43cm) or M/L (43cm-53cm). I fall at the bottom end of the M/L and this has fitted me well, with the hip belt sitting as it should to help take some of the load off the shoulders. 

The back plate and internal structure are made up of a 4mm wire frame, a removable HDPE sheet, and two aluminum stays that form a V support. Although a pack this size laden with camping and winter climbing gear is never a joy to carry, this robust system feels like it provides the necessary support when walking with such a heavy load.

A comfortable yet low-bulk back system  © UKC Gear
A comfortable yet low-bulk back system

The back panel, shoulder straps and hipbelt all have a stretch-woven snow-shedding mesh fabric over EVA foam. This provides good comfort for such a large mountaineering pack without adding unnecessary bulk when climbing or moving across technical terrain. This low profile padding also allows for extra freedom of movement when climbing and accessing a harness. Because of this requirement, the hip area does suffer slightly in comfort, since it lacks the depth of comfortable cushioning seen in most large trekking packs. I have found a small amount of pressure being put on my hip bones after carrying heavy loads, for a long period but overall I have been happy with the carrying comfort the pack has provided. For a trekking pack that you can also climb in, I think Osprey have got it about right on the padding.

For a pack this size, Osprey have done a great job producing a narrow and close-fitting bag that hugs tight to the body. When walking over technical terrain it feels stable and I haven't felt the tendency to be rocked off balance. Although I haven't actually climbed with this pack, it is clear that for its size, this design will work well both in terms of stability whilst climbing as well as avoiding unnecessary snagging on the rock when climbing or hauling.

For a pack of this size, it is relatively narrow fitting.  © UKC Gear
For a pack of this size, it is relatively narrow fitting.


The bag is essentially one main compartment, which is accessed through the top drawcord opening. Additional storage is available in the lid and in deep side pockets for some quick-access items or snow gear such as a picket. It's worth bearing in mind that, being primarily a mountaineering backpack, there are fewer additional pockets and access zips than a similar-sized trekking pack would offer.

The front shield pocket works well for storing any bulky or sharp objects like crampons or a shovel that would be too awkward to stow inside the pack, or too hard to access. It can expand out a fair amount to take a good amount of extra volume on the back. Additionally, this area uses a foam reinforcement, which will stop crampons from damaging the bag's main fabric. This panel has integrated ice-tool buckle attachments which are easy to use to secure your axes.

At the side, there are both upper and lower compression straps to reduce the volume of the bag or to secure bulky items like walking or tent poles to the side. If using these with skis on the side there are additional ski attachment loops at the bottom.

Internally there are two compression straps at the top of the main chamber which can be used to cinch down the internal load or be placed externally to secure a rope under the lid.

When climbing with the pack, there are reinforced gear attachment loops on the hipbelt, as you'll find as standard with smaller alpine packs but not so often at the Mutant Nimsdai's sort of capacity.

A reinforced three-point haul system (two at the front and single at the rear) offers simple and stable hauling if you required this in a mountaineering scenario.

Helmet carry net secures well to the top  © UKC Gear
Helmet carry net secures well to the top


The lid has a main zipped compartment which is large enough in space to store all my small and readily accessible items. Another small velcro pocket contains a handy helmet carry net which can be used to secure your helmet on top of the lid. 

The lid is also floating so that you can raise it to maximise the volume of the main compartment of the bag. If looking to go the other way and strip down the bag, the lid is removable and a flapjacket in a stowaway pocket can be used to compress the bag down and close over and protect the top opening.

Lid off and flapjacket clipped in to front buckles for heading to a climb from our camp  © UKC Gear
Lid off and flapjacket clipped in to front buckles for heading to a climb from our camp


The Mutant Nimsdai 90 is a beast of a pack that will be suitable for some big mountaineering objectives. It's well-shaped to provide a comfortable and stable experience when tackling more typically mountaineering style terrain. Robust build quality and a large simple stuff compartment mean you can really pack a lot into this pack. Some well designed features like the large robust front shield pocket work well for all your sharp, bulky and easy to access items. If you're only walking and not planning to climb then it may be a bit basic. But apart from some slight discomfort in the hips after long periods carrying a large load, I find the pack hard to fault for its intended use.

For more information ospreyeurope.com

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