Osprey Mutant Nimsdai 90 Pack Review


Our Osprey Mutant Nimsdai 90 Pack Review examines a fully featured load hauler designed with extensive input from record breaking mountaineer Nirmal ‘Nims’ Purja.  Please read on to find out more.


Nims is a Nepalese mountaineer you’ll almost certainly have heard of.  You may know of his completion of the world’s 14 8000 metre peaks in record time?  You may have heard about his historic first winter ascent of K2?  You may have read his book or heard him deliver a motivational talk? You may have heard of his environmental or charitable work? 

In recent years he has also become an influential public figure as a result of his ground breaking mountaineering achievements.  We shared details of his Project Possible and link to Osprey here.  There is also information about the groundbreaking Nepalese winter ascent of K2 here   

Nims is also an Osprey Ambassador and in the lead up to his 2020 K2 winter ascent he worked closely with the Osprey design team to produce his perfect expedition pack.  That is the Osprey Mutant Nimsdai 90.  The pack joins Osprey’s dedicated Mutant range of climbing focussed packs.  It is designed, as Osprey say, to deliver superior load carrying and exceptional stability for the most demanding Alpine objectives.  We were delighted to be asked to review one.  Please read on to find out what Paul thinks of this special pack.

Front Panel Logo


Nims Designed

I’m sure many outdoor goers would love the chance to design their own dream pack.  To work with designers and explore the intricacies of their own rucksack features and construction.  Nims, or Nimsdai as he is commonly known, had that opportunity.  

Infact, he has had a hand in all the decision making and the features and fabrics are all designed with performance in mind.  Fortunately, given his vast experience of mountaineering on the world’s highest peaks, he knows what he needs.  I was certainly excited to give this pack a test run. 

First Impressions

First impressions are of a striking design.  The Mutant 90 comes in the single colour option of Tungsten Grey with a large Nimsdai logo on the front.  The dark grey colour contrasts with orange highlights on the shoulder straps and a darker back panel.  It looks great.   


The main body of the pack is constructed from Bluesign approved 210 denier recycled nylon grid NanoFly fabric.  This is an extremely burly material coated in a PFC/PFAS free durable water repellent (DWR) coating.

Harness System 

The back comprises a rigid panel with 4mm Lightwire frame.  This is covered by an EVA padded back and Snowshed outer fabric layer.  The harness combines sculpted shoulder straps with ridged EVA foam and stretch woven mesh.  There is also a sculpted and well padded hip belt.  The hip belt has a zipped pocket for smaller items.           

Alpine Specific Features

The pack has dual tool locks for carrying two ice axes.  There is also a rope carry system and all the buckles are designed to be easily operated while wearing gloves.  

The pack is also designed to be strippable.  This includes a removable top lid and the hip belt can also be removed.  Under the main lid also sits Osprey’s superb compact FlapJacket lid. The removable lid includes a zip pocket.

Back Panel & Harness System

Compression Straps

Side compression straps combine with elasticated side pockets.  The compression straps allow the capacity to be tailored to the load.  They also, when combined with the side pockets, allow equipment to be securely carried.  This could include everything from tent poles to snow stakes.  They could even, in the high altitude context, be used to safely carry oxygen cylinders.  The pockets can also be used for smaller items like drink bottles or clothing. There are also ski carry straps.

The compression straps also link to an adjustable padded front panel that allows further storage options.  You could use this for everything from clothing to snow shovels to crampons.  When the success of the ascent relies on efficient equipment management, these additional storage options could be key factors.

Other Details        

The Mutant Nimsdai 90 is available in 2 sizes.  The small/medium has a capacity of 88 litres and the medium/large is 90 litres.  The dimensions in centimetres are 86H x 42W x 33D.  The stated weight is 2.1kgs.  The retail price is £275.

Front View With Twin Ice Axe Carry System

In Use

A Challenging Design Brief

This is a pack designed for mountaineers operating on trips where they will sometimes need a load hauler and sometimes need a more stripped down option.  It also needs to be able to stand up to harsh conditions and rough handling.  You can’t afford for your pack to fail when the success of the trip depends on it. This was my criteria when completing this Osprey Mutant Nimsdai 90 Pack Review.  

On the other hand, it needs to perform as required and not be overly complicated or heavy.  The Osprey team must surely have had a challenge with the Mutant Nimsdai 90.  I also imagine they had a challenge because Nims will have been uncompromising in his requirements. He is surely a man who knows what he wants and needs.  That’s also why collaborations of this type can be so powerful and can ultimately benefit consumers.


Osprey have chosen Bluesign approved 210 denier recycled nylon grid NanoFly fabric for the main body of the pack.  210 denier offers a good combination of durability and lightweight.  You can be confident scraping this pack over rocks or it being left outside a mountain tent in challenging weather. It will take the hits and still perform when needed. 


In line with Osprey’s sustainability commitment the fabric is made from recycled yarns with a PFC/PFAS free durable water repellent (DWR) coating.  This commitment is central to Osprey’s ethos and yet I imagine was key to Nims requirements too.  He has very much focussed his attention on minimal impact mountaineering in recent times and initiatives like his mountain clean ups aim to ensure the longevity of the mountain environment.  We talked about Osprey and sustainability here.

Fit & Carrying Comfort

The pack come in two sizes and there is some additional adjustment in fit provided by the stability straps on each shoulder strap.  Having a well fitting pack is especially important when carrying heavy loads and Osprey have worked hard to ensure this is possible.  

They have also thought carefully about a suitable harness system.  They have succeeded in producing a very comfortable pack.  The firm and yet well padded back panel combines with well shaped and comfortable shoulder straps.  Then, the broad padded hip belt both draws the pack in for stability while also allowing optimum weight distribution.  The fit can be further tailored with shoulder stability straps and a sternum strap. The hip belt has gear loops on each side.

In testing the pack it has been loaded up with many climbing ropes to simulate the kind of weights that might need to be carried on expedition.  Loaded up, and carried on many training walks.  In fact, although it hasn’t yet left the Peak District, it has been integral to my winter season training!  As I haven’t yet had the opportunity to use it on expedition, I wanted to be sure I could give a realistic view on it’s performance.  Although no one is every really going to relish carrying a very heavy and bulky pack, the Mutant 90 at least makes this as pleasant as you could hope.  

Front Expanding Load Panel

Other Features

It is clear that a lot of thought has gone into the design of all the features.  Osprey have been pack producing specialists for many decades and so it is no surprise they have thought of everything, but I’m sure Nims had his say too.  

Good pack design for me is making sure you have included what is needed and yet not being tempted to add extra bells and whistles for the sake of it.  The ideal pack, in my opinion, is therefore uncluttered, streamlined and minimalist.

Expedition Phases  

However, on expedition different phases are going to call for different requirements.  You are initially likely to be load hauling between camps.  This will certainly require carrying heavy and bulky loads.  This might also necessitate attaching equipment to the outside of the pack.  Then, later on you will want to strip off all the extras and make your pack as light and compact as possible. 

Load Carrying Features

The addition of the side compression straps, the axe carrying system, the adjustable front panel, the rope carrying system and the elasticated side pockets give infinite options.  Whether you are strapping on a set of skis, a tent, a 100 metres of rope, a sleeping mat or all these items, the Mutant Nimsdai 90 has you covered.  You also have the adjustable lid with large lid pocket to transport all the smaller items you need to find quickly. The lid also incorporates a helmet carry system.


Later, you might want to strip off as many extras as you can for that summit push.  The main lid can be removed while the smaller FlapJacket lid protects the contents of the pack (I have used Osprey’s FlapJacket system on many packs and can’t praise it enough).  Then, you can strip off any straps you don’t need and even fasten the hip belt back if you don’t want to use it.  You now have a much better option to head for the top.   

Close Profile Carry    

The pack is specifically designed to offer a close profile fit to help with efficient and safer movement.  Having the pack close to the body and stable is really important when moving over technical ground.  For its capacity, Osprey have really worked the shape to allow this.  Although you know you are wearing a 90 litre load hauler, it feels much more compact on your back.  It also feels very stable.  I deliberately took the loaded with ropes Mutant on some technical scrambling ground and its stability is very impressive.

Side Compression System, Ski Carry & Storage Pockets


Although I haven’t yet been able to test this pack on expedition, I feel confident I have re-created enough of the type of usage to effectively complete this Osprey Mutant Nimsdai 90 Pack Review.  The reality is I couldn’t be more impressed.  Osprey (and Nims) have produced a large and durable load carrier with all the features needed for effective expedition use.  

It is actually hard to sufficiently explain how you can carry something this large loaded with many kilos and yet it doesn’t feel the beast of burden you would expect.  You really need to try it to fully appreciate its performance.

This is a pack that is only going to be needed by certain people with certain objectives, but if that’s you then I really can’t recommend it enough.  Well done to Osprey for producing specialist items of this type and I hope you get the chance to need one for a future trip.  In fact, maybe you might want to start planning a trip just so you have reason to use one!  

Full details on the Mutant Nimsdai 90 are available on the Osprey website here.  Please also check out the video below which features Nims sharing the features (and his obvious enthusiasm) for the pack.

Osprey Reviews

We hope you found this Osprey Mutant Nimsdai 90 Pack Review useful. We have been privileged to work with Osprey for many years and have previously reviewed many of their products.  There are lots available on the review section of our website.  A few examples include our review of their Nanofly 20 pack here, their Talon 55 here and here.  We also have other Osprey pack reviews in the pipeline so please keep checking back.