An incredibly breathable, impressively warm, naturally odour-resistant hoodie built for proper output in cold weather. Pricey, yes – but undeniably brilliant.

Icebreaker Merino Blend 200 Realfleece Descender

Ideal for: Trail running, bikepacking, hiking and fastpacking

Not suitable for: Nothing — this fleece can do it all!

The Icebreaker Merino Blend 200 Realfleece Descender Long Sleeve Zip Hoodie is a high-performance midlayer made for cold-weather trail running, fastpacking and active pursuits in the hills. Designed with a 60/40 blend of Tencel and merino wool, it’s stretchy, breathable, warm and odour-resistant. Weighing just 273g in size medium and packing down neatly, it’s ideal for UK conditions – whether you’re slogging up snow-dusted ridges or bouncing through wet woodlands. The £160 price tag is high, but if you’re often out in the elements, its breathability and comfort levels are genuinely next level.

Icebreaker Merino Blend 200 Realfleece Descender midlayer review

New Zealand-based Icebreaker have built their reputation on pioneering the use of natural fibres in performance clothing – long before ‘sustainability’ became a buzzword. Since 1995, they’ve been turning merino wool into premium base and midlayers, prioritising natural performance over synthetic quick fixes. Their ethos has always been rooted in simplicity, longevity, and a deep respect for the outdoors – values that resonate with those of us who spend a lot of time in the hills.

At the heart of Icebreaker’s success is their commitment to merino wool – a remarkable natural fibre that’s uniquely suited to outdoor adventure. Sourced from merino sheep, which roam the high country of New Zealand’s Southern Alps, this wool is significantly finer and softer than traditional sheep’s wool. That means it’s itch-free against the skin, lightweight, and extremely comfortable – all crucial things when you’re wearing it for hours on end.

But comfort’s only half the story. What really sets merino apart is its performance. It insulates brilliantly – keeping you warm in the cold – but it also breathes and wicks moisture like a champ, helping you stay dry when you’re working hard. It’s naturally odour-resistant too, which is a game-changer on multi-day trips where washing isn’t an option. And because it’s biodegradable and renewable, it’s a far more sustainable option than synthetics, which rely on petrochemicals and can shed microplastics into the environment.

Icebreaker were among the first to harness merino’s potential in technical garments, and they’ve spent decades refining their blends to get the most out of this material. The result is a range of kit – like the Realfleece Descender – that’s built for proper use in the real world. Layers that work with your body, not against it. Layers that stay warm when damp, breathe when you’re working, and keep smelling fresh even after back-to-back days on the trail. For anyone spending time outdoors in the UK, it’s easy to see why merino – and Icebreaker – have such a strong following.

A midlayer that breathes

Their Merino Blend 200 Realfleece Descender Long Sleeve Zip Hoodie continues this theme. Designed for high-output activities in cold conditions – like winter trail running, hiking, or fastpacking – it’s a genuinely technical piece built from a clever 60/40 blend of Tencel and merino wool. That combo makes it impressively soft, durable, and breathable, while still bringing the natural thermoregulation and odour-resistance merino is known for. At 273 grams in medium, it’s properly light for a natural fibre midlayer – and although it’ll set you back £160, Icebreaker have made something that punches well above its weight.

Price-wise, it sits right at the top end of the market. Compared to budget synthetic options like the Mountain Warehouse Snowdon II (£9.99), it’s astronomically expensive – but offers far better breathability, odour resistance and performance. It’s priced slightly above The North Face’s synthetic Futurefleece (£135), which is also light and breathable but lacks the environmental credentials and comfort of merino. Meanwhile, Columbia’s Sequoia Grove (£65) offers decent value but nowhere near the same performance-to-weight ratio. In short: if sustainability, warmth and breathability matter most – and you don’t mind the price tag – the Descender Hoodie is in a class of its own.

How we tested the Icebreaker Descender

We’ve been wearing this fleece across the chillier months of autumn, winter and spring – and it’s seen some miles. From long trail runs along the Thames Valley to a full weekend scrambling up Jacob’s Ladder in the Brecon Beacons, to two rainy nights wild camping on Dartmoor, we’ve worn it in wind, rain, sun and sub-zero temps. We layered it under a Mountain Equipment Lightline, paired it with a waterproof on Dartmoor, and wore it solo on fast-paced runs. We’ve sweated through it, let it soak, slept in it – and we’ve come away genuinely impressed.

Features that matter

What makes the Icebreaker Realfleece Descender stand out is how considered every detail feels – each feature pulling its weight to create a midlayer that’s genuinely fit for purpose.

The fabric is, without exaggeration, one of the most comfortable we’ve ever worn in a midlayer. The 60/40 Tencel and merino blend brings together the best of both worlds: it’s soft against the skin, stretchy enough to move with you, and absurdly breathable. On long trail runs and uphill slogs, we were constantly impressed by how well it managed heat and moisture. There’s no sense of dampness or cling, and we never once felt like we were about to overheat – even when pushing hard. It’s the kind of material that lets you forget about your kit and just get on with the task at hand.

The minimalist design supports this idea of movement-first function. There are no hip pockets – which at first feels like a miss, until you realise how much better it is not to have things bouncing around your waist while running or jammed under a harness. Instead, you get a single napoleon chest pocket that sits flat, stays put, and is ideal for stashing smaller items like gels, keys or a card.

The zip setup is equally well thought through. The toggles are short and textured, meaning they’re easy to grab even with gloves on and won’t flap about or rattle when you’re on the move. We didn’t have a single snagging issue throughout testing. The only trade-off is that because the fabric is so lightweight, zipping it up smoothly does require two hands – but it’s a small concession for such a breathable and low-bulk layer.

Thumb loops are another great addition. When in use, they keep the sleeves locked in place and prevent any bunching during high-movement activities like scrambling or fast hiking. When you’re not using the loops, the wrists are a touch baggy and can bounce around a bit – but rolling them up once solves the issue neatly. It actually feels like an intentional bit of design flexibility: looser cuffs for airflow, or locked-in sleeves when needed.

The seamless shoulders are one of those small details that make a huge difference over time. We wore this under heavy packs on multi-day trips and never once felt the fabric dig in or rub – even when everything else was starting to ache. The hood, too, deserves credit: it fits snugly, doesn’t get caught in the wind, and layers neatly under a shell or beanie, giving you reliable coverage without faff.

And while natural fabrics aren’t usually known for their quick drying times, this one punches well above its weight. Even after hours of Dartmoor drizzle, it dried out overnight simply by stuffing it inside a sleeping bag. That meant we weren’t stuck with that awful damp-chill feeling you often get from soggy synthetics, and could head out the next day feeling warm and dry. The real bonus, though, is that because of the merino content, it still kept us warm even while damp – something synthetic layers rarely manage. It’s a reassuring bit of performance when you’re out in unpredictable British weather and can’t count on staying completely dry.

Every element of the Descender has been built with high-output adventures in mind – and when it all comes together, it’s easy to see why this isn’t just another fleece. It’s an investment piece for people who get outside a lot and need their gear to keep up.

All-weather performance in the UK

From frosty mornings in the Brecon Beacons to rainy nights on Dartmoor, the Icebreaker Merino Blend 200 Realfleece Descender never let us down. It provided proper warmth in single-digit temps – even when standing still – and just the right amount of ventilation when we were on the move. Layered under a down jacket, it kept us toasty during chilly coffee breaks on windswept ridgelines. Worn beneath a hardshell, it managed to breathe well enough that we never felt clammy, even when the outer layer was soaked through. It’s that kind of consistent, all-conditions performance that makes it feel tailor-made for British adventures.

And let’s be honest – the UK can throw it all at you in a single outing. Cold mornings give way to muggy climbs, sunshine turns to hail, and trails can go from bone-dry to bog in a matter of hours. That’s where this midlayer really shines. The breathability is best-in-class, making it perfect for activities like trail running, fell running and fastpacking – pursuits where you’re generating heat one minute and battling windchill the next. It adapts. It never feels too hot or too cold. It’s a true ‘set-it-and-forget-it’ fleece.

We found it especially useful during those days where the weather can’t make its mind up – the sort of days that define British hillwalking and winter running. It keeps you warm when you need it, vents when you’re pushing hard, and doesn’t cling when damp. Even after getting caught in heavy rain on Dartmoor, it dried out fast overnight and didn’t leave us with that clingy, cold feeling you often get with damp synthetic layers.

If you’re moving fast in the hills or ticking off miles on foot across the UK’s rugged and unpredictable terrain, this midlayer just works. It’s built for the kind of conditions we face regularly – not just alpine extremes or bluebird days – and that’s why it’s earned a regular spot in our kit bag.

Icebreaker Realfleece Descender FAQs

Very. For its weight, the warmth is remarkable. Paired with a base layer, it’s enough for sub-zero runs. Worn under a down jacket, it works in properly frigid conditions. It’s one of the warmest midlayers we’ve used in the UK, especially for how light it is.
In a word: exceptional. This is easily one of the most breathable fleeces we’ve ever tested. Whether running hard uphill or moving fast with a pack, we never once felt clammy or stuffy. It’s built for movement, and it shows.
If you’re regularly outdoors in cold weather – running, hiking or fastpacking – then yes, absolutely. It’s expensive, but the comfort, performance and low-maintenance wearability are hard to match. For casual users, cheaper fleeces may suffice. But for the committed, this is money well spent.

TheIcebreaker Realfleece Descender: Our thoughts in a nutshell

If you’re regularly running, hiking or fastpacking in the UK and want a fleece that can handle sweat, wind and chill – and won’t need washing every time you wear it – then the Icebreaker Merino Blend 200 Realfleece Descender is a fantastic choice. It’s not cheap, and it’s probably overkill for casual dog walks or pub hikes. But if you’re serious about moving fast in cold weather and you value sustainability, breathability and low maintenance, it’s hard to beat.

Yes, we wish it cost a bit less. But after using it across three seasons, we’d argue the price is justified – at least for those who’ll actually use it to its full potential. For trail runners, fell runners, fastpackers and winter hikers, this is up there with the best..

Icebreaker Merino Blend 200 Realfleece Descender midlayer review: the breathable fleece that doesn’t quit