Gear Reviews

Mountain Equipment Superflux insulated jacket review

The Mountain Equipment Superflux – is it worth the money?

The Mountain Equipment Superflux jacket is a medium-weight mid-layer designed to keep you warm whether you’re on the move or working as a belay in mountain conditions. Filled with POLARLOFT (Mountain Equipment’s patented insulation), the jacket has a down-like feel without the cons of down! Or so they say.

This jacket is a recent addition to my growing collection of insulated mid-layers and, so far, I love it. But before you decide if this is right for you, let’s get into this review.

Mountain Equipment logo.
My first, and not my last, Mountain Equipment jacket.

Note: the testing for this review was conducted on both the North Slope of Alaska and in an English winter hence the variety of images from different climates.

What we think

I’m a newcomer to Mountain Equipment outdoor gear. For a number of years, my go-to options have been the likes of the Rab Cirrus Flex hoody, the North Face, and offerings from Red Fox (a Russian equipment manufacturer that makes the kind of rugged gear I need for expeditions into the extreme cold). In recent months, and with my planned ski across the Alaskan North Slope, I decided to test some alternatives hence why I’m writing I’m writing this review.

And I’m impressed. For a reasonable price, the Superflux delivers on the many promises made by Mountain Equipment. My two key criteria for any jacket are:

  1. It has to keep me warm;
  2. Needs to be reasonably packable.

And the Superflux is both. We’ll walk through the rest of this post in just a moment, but for now, let’s just say I’ve been impressed with this jacket since buying it.

Even at the bus stop, on a cold day, the Superflux looks good,


Mountain Equipment describes this jacket as an all-weather option and, broadly, I agree but you do need to be aware that, whilst water resistant this jacket won’t keep you dry long in a heavy downpour. But you already knew that.

What goes into the Superflux build?


Made from 40 Denier (40D) DRILITE LOFT, the shell’s outer fabric carries a claim that it’s totally windproof and, from my recent winter hikes I  have to agree with this statement. On one particular day, I wore the jacket in one of the howling gales of December and there was none of the ‘seeping cold’ that comes with some ‘lesser’ mid-layers. On this front, Mountain Equipment’s statement stood the test of a furious English winter’s day.

As well as being windproof, the outer is also water-resistant (not waterproof, an important point to note which we’ll look at soon). For anyone with an environmental conscience, you’ll be pleased to hear Mountain Equipment only use PFC-free fabrics in the construction process and the DWR shell is pretty much as close to carbon neutral as you can get.


The Superflux fill aka Featherless insulation provides a more than adequate degree of protection from cold weather. The only quibble I have with the advertising is this: ME says the jacket is good for ski touring, which it is but only as an additional layer you pull on when at a halt. If you try to ski in this jacket you’ll get hot fast.

I wore this jacket for a gentle hike on a day when the temperature hit -10C and within a short space of time my body was overheating. What does this mean for you? The POLARLOFT fill works very well but don’t be tempted to wear it if you’re on a hard hike or engaged in arduous activity – use it only when you’re on a pause or in your tent.


One aspect of the Superflux I really like is the simplicity. Unlike some of the other mid-layers and shell jackets available (like the Apricoat Eco down jacket), there are no ridiculous features you’re never likely to use (I mean, a pillow inside the hood? What a waste of space).

The jacket consists of:

  1. The jacket’s body can be best described as a roomy, not athletic fit (a word of caution if you’re looking for an insulated jacket that makes you look sleek and sporty).
  2. Two large hand warmer-style pockets on the outside and one chest pocket that has ample space for bulkier items such as a GPS, InReach, etc.
  3. A very large, adjustable hood that is more than adequate for covering a helmet, or protecting my massive head from the elements.
The hood has plenty of room for a helmet. Mountain Equipment has hidden the draw cord adjusters between the jacket’s layers which can make the adjustment, and repairs, fiddly. No, I wasn’t asleep – the wind was in my eyes!

And I have to admit to liking the fit as I’m at an age where having my biceps straining the arm material is no longer high on my list of priorities when I’m hiking! In fact, I like clothing that has a more relaxed and comfortable fit that allows me to add and remove additional layers as required.

As you’d expect, the construction of the Superflux is what is known as ‘stitched-through quilted’ to ensure the POLARLOFT fill remains in place to prevent cold spots (the chill you feel when the fill balls up or shifts to leave uninsulated areas pressed against your body)

The adjustable hem draw cords are important to me. I’ve owned many jackets with elasticated hems and I find the tension allows the jacket to ride up when I’m moving, unlike draw cords which can be tailored to an individual’s build and pulled tight to prevent ‘rising’. Having a good fit also helps prevent heat loss which is vital when you’re in the cold

Superflux hem drawcords
The Superflux hem drawcord are easy to adjust even when wearing gloves.

Likewise, the draw cords on the hood can be adjusted to your personal needs and can easily accommodate a mountaineering helmet.

The hood is adjustable – there are two draw cords for controlling the size of the aperture and a Velcro adjuster on the rear used to alter the fit to either accommodate a helmet or for tailoring a snug fit to your head.

hood adjuster.
The hood adjustment uses a simple, but effective, velcro strip.

And in a final nod to efficiency, the entire jacket can be packed in the hand pocket (which has a couple of carry loops for karabiners… but I’d advise you never to clip these to your rucksack unless you’re looking to test their security and reliability).

The are only two issues I have with the design of the Superflux:

  1. The inner security pocket is a little large and deep for my liking. The bottom of the pocket sits in line with the top of my rib cage and small items can be trapped, or pressed hard against my body when wearing a harness. My personal preference is for higher, shallower inner pockets.
  2. The toggles for the hood draw cord are stitched inside the skin of the jacket. On one hand, this helps reduce the risk of damage, but if the toggle breaks and needs to be replaced you’ll have to unstitch a section of the jacket to get to it.
How heavy is the Superflux jacket?

A mere 580g, or 20.5 oz. Not the lightest of jackets but that’s not surprising considering how warm it is.

Superflux innner pocket.
The inner pocket provides a good storage capacity for gear and the opening is wide enough for my huge hands to fit in with ease.


I am very impressed with the performance of this jacket. It’s not the warmest I’ve ever worn but, considering the moderate weight, the warmth-to-weight ratio is excellent and I will be testing it out in more extreme cold weather in Alaska.


Filled with 246g of POLARLOFT, what Mountain Equipment calls a ‘featherless fill’, this jacket provides exceptional heat retention and insulation qualities making it perfect for activities where you’re static or moving at a slow pace in cold weather. It’s an ideal layer to pull on when you need to pop out of your tent to pay nature a fleeting visit.

I tested it to -10C and had no issues. If you’re going to be in colder climates you might want to add an extra layer below the more than generous cut of the jacket.


At 20oz (580g) this is most definitely a mid-weight jacket, but it’s not so heavy to be discounted from an ultra-lightweight hike. The weight and fill make it a great option for winter activities, but if you need something for warmer weather activities you’d be better off looking at something like one of Fjern’s offerings or reading our Montane Icarus jacket review.

So, if you’re planning cold-weather activities this is the jacket for you. If you’re a fastpacker who needs only a thin layer then you need to pick another option.

Water Resistance

You already know traditional down jackets do not perform well when moist unless the fill is aquaphobic (a type of down treated with a water-repellent coating). Untreated down absorbs moisture fast and loses its ability to loft and insulate you from the cold. There are no such issues with the Superflux.

The large size of this jacket is packed with 246g of Bluesign® approved POLARLOFT® Featherless insulation by 3M. This material actively repels water to keep you dry. Assuming any moisture penetrates through the DWR shell.

It’s not 100% waterproof, but the combination of the outer and fill makes this jacket highly resistant to all but the heaviest of downpours, although I wouldn’t take the risk of wearing a hardshell over the top when the Heavens open up.

All in all, the jacket has excellent water resistance.


The cut of the jacket is generous and incredibly comfortable. There is plenty of room to add additional layers without looking and feeling like the Michelin Man or Mr. Stay Puft, the giant marshmallow man from the film Ghostbusters.

The arms seem a little on the long side and when combined with the elasticated cuffs they allow you to extend your reach without riding up beyond your wrists. The cuffs also prevent the sleeves from sagging down over your hands.

As it’s one of the bulkier jackets we’ve reviewed, the Superflux can feel a little cumbersome and restrictive when you pull a shell layer over the top. That said, this jacket was designed for cold weather and will keep you warm and comfortable in all but the most extreme cold environments.


Superflux compressed
The Superflux compresses to a reasonable size.

For some reason, many of my friends make a big deal of compressibility (Jake and I regularly compare sizes… of compressed jackets). But the reality is you’ll only need a jacket that squeezes down to the size of a satsuma if you’re the most zealous of fastpackers.

When compressed into the chest pocket, the Superflux measures 35cm by 15cm, and I find it hard to believe any hiker couldn’t find space to fit it into a rucksack. If you really feel the need to go smaller, buy a lighter and probably less well-insulated jacket, or use a compression sack to make it even smaller.

How does the Superflux compare to other insulated jackets?

The Superflux is an excellent alternative to some of the more expensive mid-layers on the market. Whilst it’s pricier than the Rab Cirrus it has more insulation making it a better option for those times when you’re static and the weather is cold! The other jacket we have to flag up as a good alternative is the Arc’ Teryx Atom LT which is Jake’s preferred choice for hikes out in the Scottish wilds (that review is worth taking your time to read).

To my mind, the only other jacket I can think of that comes anywhere near as capable as the SuperFlux is the Montane Icarus (review here). I’ve used this in Alaska where the temperatures dipped to around -50C and as an insulating layer, it performed well above my expectations (which was a stroke of good luck considering the freak weather we experienced).

Should you buy the Superflux?

The Superflux jacket is one of the best I’ve reviewed so far. It’s comfortable and roomy with an excellent weight-to-warmth ratio which is a feature I find lacking in some other jackets we’ve looked at on TrekSumo. There’s plenty of room for additional layers and ample storage in the three generously sized pockets. It’s a great insulating layer for cold weather activities such as mountain hiking, possibly cross-country skiing (I’ll let you know about this when I get back in March), where you’re static or moving slowly. And the price is good – around $210/£170 – or less in the UK if you pick up a discount from Go Outdoors.

superflux pockets
The jacket has large pockets which are ideal for warming your hands.

Buy the Mountain Equipment Superflux jacket if: 

  • You need a generously cut jacket that allows you to add layers;
  • Cold weather hikes and mountaineering are your choices of activity;
  • You need a jacket that will keep you warm when static.

Don’t buy this jacket if:

  • You need a mid-layer to wear whilst on a fast-moving hike;
  • Having large amounts of storage is important;
  • 580g/20 oz is too heavy.

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