Designed for climbing and winter peakbagging, the Osprey Mutant 38 Backpack only weighs 2 pounds 15 ounces (size medium), and has a clean streamlined design optimized for rock and ice climbing that won’t slow you down over rough scrambling or more technical routes.
- Dual ice axe/tool attachments (top and bottom)
- Climbing rack loops on hip belt
- Z compression straps
- Top compression strap and rope carry
- Removable tri-fold bivi pad
- Removable framesheet
- Removable/floating lid top pockets
- 3 point haul system
- Spindrift collar
- Dual snow picket/avalanche probe pockets
- Load lifters
- Adjustable sternum strap with emergency whistle buckle
- Fixed Ergopull hip belt with reverse wrap capability when wearing a climbing harness
- Padded shoulder straps with elastic keeper straps
- Hydration reservoir pocket and left/right hydration ports
The Mutant is primarily a winter climbing or snowsport pack. You can tell this immediately by looking at the backpad on the pack which is made out of thermo-molded EVA foam. It doesn’t have much in the way of ventilation because in winter you want your backpack to mold around your back and provide you with additional insulation.
The other thing about this backpad is that it’s annealed directly to the main compartment of the pack without any kind of gap between the two. This keeps the center of gravity of the pack very close to your back so it feels like it’s an extension of your body and moves when you do. This is the exactly kind of fit you want for climbing, scrambling or mountaineering to avoid burning out your muscles on vertical ascents.
The Mutant also comes with two additional internal suspension components: a bivi pad together with a plastic framesheet. Together they provide the EVA backpad with a little extra stiffness and help improve the transfer of weight from the main compartment to the hip belt. They also prevent the back of the pack from collapsing on itself when the main compartment is not packed tight, which would shorten the pack’s torso length and throw off its fit.
The bivi pad and the framesheet are optional and removable if you want to save a little pack weight, but you should only do this when the main compartment is packed tight and the EVA backpad can’t collapse on itself.
- The plastic framesheet weighs 5.2 ounces.
- The tri-fold bivi pad weighs 2.5 ounces and is 1.4 cm deep when folded together.
Design-wise, a plastic framesheet is a normal component in a pack of this size and this one does a great job in transferring the load to lumbar pad at the base of the backpad, which is sewn into the hip belt.
The bivi pad is rather unusual though and not something I’ve seen on the other Osprey packs I’ve reviewed in the past. In this pack, it’s primary use is as a shim to secure the plastic framesheet in place in its interior pocket and prevent it from buckling when the pack in not tightly loaded. It is not as useful as one might hope as a bivy pad under a sleeping bag because it’s only 24 inches long and barely reaches from my shoulders to my hips when I lie on top of it (I have a very short torso). It’s also way too thin to provide any cushion or thermal insulation and not something I’d recommend that anyone use for anything except a sit pad.
The Mutant’s hip belt is a significantly more functional and has some nice climber specific features. Like other Osprey packs, the Mutant uses an ErgoPull hip belt which I really like because you can get a tight and secure fit. The hip belt itself is not heavily padded nor does it have to be for the 30-ish pound loads that you are likely to carry with this pack.
If you are climbing and using a harness, the hip belt can be wrapped around the back of the pack and secured to keep it out of your way. There are also racking loops sewn into the hip belt that you can suspend gear from, though you’d probably use a real climbing rack or harness for anything serious.
Unfortunately, the hip belt only comes in fixed lengths corresponding to torso lengths and is not replaceable if you happen to be short, but say, have a large waistline. I hate it when manufacturers design packs like this, so be forewarned and make sure that you can get the fit you want before you set your heart on buying this pack. I wish more backpack manufacturers provided mix and match hip belts in different sizes with their packs, but unfortunately I expect hell will freeze over first.
Compression System and External Attachment Points
The Mutant has a minimal compression system that’s primarily intended for compression and not for strapping external gear to the outside of the pack. This makes sense when you consider that it is designed for specifically for technical climbing or rock scrambling.
What compression there is, is limited to a pair of Z compression straps on the sides of pack which are designed to save weight but not to attach gear.
In addition, the pack has a floating lid which can be used to sandwich gear between the top pocket and the main compartment. The floating lid is removable, potentially saving another 6.3 ounces of pack weight, but doing so would remove a considerable amount of storage space from the pack and is probably not worth doing.
The Mutant has 38 liters of storage space split between a main compartment and a floating lid, which has one external pocket and one internal pocket. There is an 8.5 inch spindrift collar at the top of the main compartment that you can stuff more gear into as well.
The only other external storage on the Mutant are a pair of snow picket sleeves on the sides of the pack.
The Mutant doesn’t have any side pockets for water bottles, but it does have an internal hydration pocket and dual hydration ports to let you run a hose to the shoulder straps. However, in testing the Mutant with a hydration bladder, I found that a full reservoir can be felt through the EVA backpad when the main compartment is stuffed tight, even when the plastic framesheet and bivi pad are in place.
Emptying the pack or drinking down the reservoir relieves the discomfort, but it makes packing the pack a little tricky if you have a lot of gear to carry and you need to carry a lot of water. I don’t use hydration reservoirs anymore because I’ve experienced too many leaks with them in the past, so my workaround is to simply carry water bottles on top of my other gear for easy accessibility.
The Osprey Mutant 38 is an exceptionally comfortable backpack to carry with an excellent hip belt system and lumbar padding designed to transfer weight off of your shoulders and onto your hips. But it really is just intended for climbers or and not backpackers. If you are a rock or ice climber, and you like a form-fitting technical pack feels like it’s an extension of your body, this is the pack for you.
- Extremely good weight to hip belt load transfer
- Streamlined design, perfect for rock climbing and snow sports
- Excellent compression system
- Floating lid with spindrift collar
- Full hydration reservoir can interfere with packing and fit
- Hip belt is not replaceable, and is based on torso lemgth.
- Bivi pad is too thin and short to be used under a sleeping bag
Disclosure: Osprey Packs provided SectionHiker.com with a Mutant 38 for this review.Editor's note: Help support this site by making your next gear purchase through one of the links above. Click a link, buy what you need, and the seller will contribute a portion of the purchase price to support SectionHiker's unsponsored gear reviews, articles, and hiking guides.
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