Osprey Mutant 38 Review

25th Oct 2018



I have accumulated quite a number of rucksacks at Peak Mountaineering HQ and they all serve different purposes. However, for my mountain activities the ones I seem to reach for most are usually in the 35-40 litre range.  This size will carry enough for an overnight wild camp,  hold the hardware and bivvy gear for an Alpine route, carry everything needed for a day of multi pitching and is flexible enough to make a good cragging or winter pack.  I would say that if a climber was choosing just one size of pack there is a lot to be said for this being the size.


Osprey recently released the 5th generation of their much loved Mutant 38 and this climbing focussed pack fits bang in the middle of that size range sweet spot.  I have previously tested their Mutant 28, Mutant 22 and Variant 38 and was really keen to give this pack a test.  It certainly hasn’t disappointed........



Osprey market the Mutant 38 as a dedicated climbing pack.  Infact, their full description is ‘a reliable, intelligently featured climbing pack for year round ascents.’  Hence, it is designed for all conditions and the feature set is broad enough to tick all bases.


The Mutant 38 is made from durable 420HD nylon packcloth with a snow shedding back panel and reinforced base.  It is a ‘traditional’ style climbing pack with single main compartment and floating lid with lid pocket.  However, the lid is also removable and Osprey have added a second low profile ‘mini’ lid (they call it a Flap Jacket) that can be used instead.


The back panel is padded and there is a removable HDPE framesheet and alloy stiffener.  There are contoured and ventilated padded shoulder straps and a padded waist belt that can be ‘reverse wrapped’ to keep it out of the way when climbing.  The waist belt also features integrated gear loops.  Finally, to finish up the harness system there is a sternum strap with emergency whistle.


On the front of the Mutant there are Dual Lock ice axe attachments, daisy chains for equipment attachment, 3 point haul system, side compression straps, an internal top lid compression strap, side ski carry system and an integrated helmet carry system.  Finally, there is a key attachment in the lid pocket and the pack is hydration system compatible.  The pack weighs 1.28kgs in size m/l and comes in 2 sizes (s/m and m/l) although this weight can be reduced by stripping back some features.


In Use

I have used the Mutant extensively over the last 4 months.  This has included carrying the pack full of kit to crags, overnight camping trips and long multi-pitch mountain days.  It has been my main pack over a busy guiding summer.  


The first thing to mention about the Mutant 38 is that it is a great looking rucksack.  The new model has a more streamlined profile ideal for a climbing pack and, despite its packed feature list, it has a neat and uncluttered appearance.  I was sent a test model in black colour and it looks great.  There is also a blue colour (called ‘blue fire’) available.  


The Mutant feels solid and well built due to the combination of the rigid back panel and the tough construction fabrics.  The back has a padded and shaped back with internal HDPE framesheet and dual mouldable alloy stays.  Osprey have updated this for this 5th generation model and I think they have done a great job - it offers a very comfortable and supportive carry even when packing very heavy loads.  I have tried the pack with quite heavy loads and it feels very well balanced and stable.


The shoulder straps offer a good balance between comfort, a streamlined profile and breathability and the waist belt is supportive enough to take some of the load off your shoulders.  As mentioned above, if needed the waist belt can also be fastened behind the pack which can be useful when climbing with a pack on, but I like that Osprey decided to keep this as a permanently attached waist belt rather than trying to offer a removable one that can get over complicated and not perform as well.  


I have tried the pack with and without the removable frame sheet and alloy stays.  My preference is to use it with them in but it is good to have the choice.  Removing them saves some weight and some people prefer the softer feel of a less rigid back and so the best option is to play around with the different options and make your own choice.       


The style is the traditional single compartment with top lid design and Osprey have done this for good reason - it is a style that works really well because it is easy to load and unload (providing you have planned out how everything is packed inside) and the top lid, besides being useful additional storage space, also offers weather protection and maximum storage space for the sack volume.  


There are times when the amount you need to carry is greater than the pack volume and so having some additional storage options is useful - and this is particularly relevant if you are carrying a loaded pack into a climb but you will then be using some items like ropes and helmet for the climb itself.  In this scenario you are well catered for with the Mutant 38.  There is an under lid compression strap that will securely hold a rope, a clever integrated helmet carry system, daisy chains on the front for attaching other items such as a sleep mat and finally there are side compression straps that could secure a bivvy tent or similar items.


Of course, at other times you may want to strip the pack to make it as light and simple as possible.  In this case you could take the lid off and Osprey have added their Flap Jacket option.  This is essentially a mini lid that replaces the main lid and seals the top entrance to the pack.  I have experienced this on various Osprey packs and, although I admit I originally thought it was likely to be a gimmick, having used it a lot I can definitely now give it a big thumbs up.  It means that if you are climbing with the pack there is loads of room to tip your head back and it gives a neat uncluttered profile.  It also saves some pack weight.  


As you would expect, all the exterior attachments work exactly as you would wish.  The side compression straps have glove friendly buckles and have been redesigned since the last version of the Mutant.  The gear loops on the waist belt sit well and, although I must admit I don’t really use these on climbing packs, they are there if you want them.  The Dual Lock ice axe attachments efficiently secure ice tools and, although I have so far only tried the ski holders to assess them for this review, they work exactly as I would expect.  I haven’t yet tried the haul loop system and this really isn’t an option I see myself using, but it is there if needed and seems like it will work exactly as required.  


The 420HD fabric has easily shrugged off all the use and abuse I have thrown at the pack so far.  Infact, it still looks as good as new.  Osprey have wisely added a reinforced base and everything is put together with their typical excellent build quality and attention to detail.  This pack will certainly stand up to tough use.  


This durability is perhaps reflected in the 1.28kg pack weight which certainly puts the Mutant 38 around the middle of the weight range for packs of this type.  This can be helped by stripping off the lid and I would again emphasise that for a durable climbing pack the Mutant holds its own really well in the modern climbing pack genre. 



If you were going to choose one general purpose, all season, ski capable and mid size climbing pack then I suggest you look first at the Osprey Mutant 38.  Osprey have taken a classic climbing pack and, in its 5th generation incarnation, made it even better.  It manages, by a combination of great design and attention to detail manufacture, to be a very capable pack suitable for hard use by a broad range of users.  It has performed with aplomb in every situation I have used it and I look forward to us enjoying many more great adventures together.  Another great Osprey offering which I think, at a RRP of £125, also offers great value.


Posted by Paul