Rab Nexus Fleece review: the grid midlayer that earns its keep on the move

The Rab Nexus is one of the fleeces people keep recommending to me, and it comes up again and again in the "what should I layer under my waterproof" conversations that never really end on the hills. It is a UK favourite for a reason. But it is also the sort of fleece that gets bought for the wrong job, so before anything else, let me be straight about what it is.

The Nexus is a grid fleece. That makes it an active midlayer, something you wear while you are working, not a cosy fleece you throw on at the summit to get warm. If you want warmth, this is not the one, and I will point you at the right pieces below. If you run hot on the climbs and keep drenching your baselayer, this is exactly the category you should be looking at.

This is a clear-eyed look at what the specs say, how the fabric is built, how it compares to the pieces it sits next to, and where I would and would not spend the money.

For the wider picture, this review links up to the best hiking fleeces roundup and the fleeces hub. This piece stays on the Nexus.

What the Nexus is (and is not)

Rab builds the Nexus around a fabric called Thermic G, a grid-backed recycled polyester fleece. The whole design brief is regulation, not maximum warmth: keep you comfortable while your output is swinging up and down, breathe hard when you are climbing, and hold just enough warmth when you ease off.

So the honest framing, up front:

• It is a lightweight active midlayer, a layering piece, a "wear it moving" fleece with strong warmth-for-weight
• It is not a warm fleece. It is thin, and it will not keep you warm standing around in the cold on its own. That is not a fault, it is the category

If you have read the fleeces roundup, you will have seen the split I keep coming back to: high-loft fleeces for warmth, grid fleeces for moving. The Nexus is firmly in the second camp.

Specs

Price

Pull-On around £70, Hoody around £80

Fabric

Thermic G, 178gsm grid-backed recycled polyester fleece

Weight

Pull-On around 252g (M), Hoody around 308g (M)

Fit

Regular

Front

Pull-On: deep venting half zip. Hoody: full-length YKK VISLON zip with zip guard

Pockets

Pull-On: zipped chest pocket. Hoody: two zipped mesh-lined hand pockets

Collar / hood

Pull-On: soft close-fitting collar. Hoody: helmet-compatible hood

Cuffs

Double cuffs

Recycled content

Around 86% recycled overall, 94% of the fabric by weight

Chemistry

Fluorocarbon (PFAS) free

Variants

Pull-On and Hoody; men's and women's

A couple of these numbers do the talking. Around 250g for the Pull-On in a medium is light for a fleece that still reads as a proper midlayer, and it is where the warmth-for-weight reputation comes from. The 178gsm fabric weight tells you the same story from the other direction: this is a thin fleece by design.

The grid construction, and why it breathes

This is the part that matters, because the grid is the whole point of the Nexus.

A standard fleece is a continuous flat pile: a solid wall of fibres across the whole inside face. It is warm and it is cosy, but that unbroken surface also traps moisture and holds heat you may not want when you are working hard. A grid fleece breaks that surface up. Instead of a solid face, you get raised blocks or pillars of pile with channels of thin, open fabric running between them, a waffle or grid pattern against your skin or baselayer.

Those channels are what make it breathe. They give sweat vapour a route out and give hot air somewhere to escape rather than sitting against you, so on a hard climb the fleece dumps heat instead of cooking you. The raised pillars still trap air, so you keep useful warmth-for-weight, but you get it with far more of the fabric being thin, open and quick to move moisture. The other bonus is drying speed: less solid fabric means less to hold water, so a grid fleece dries fast after a sweaty push or a shower that got through.

The trade is baked in. Break up the pile to breathe and you have, by definition, less fabric trapping air, so a grid fleece is never going to match a lofted fleece for standing-still warmth. Rab's Thermic G is tuned squarely for the active end of that trade. If you want the warm end instead, that is a different fabric and a different fleece.

Worn on the move, or under a shell

The Nexus is happiest in two situations, and they are the two that describe most UK hill days.

On the move, as your outer layer. Dry, cool, breezy-but-not-brutal: the Nexus on its own over a baselayer is close to ideal for a fast walk or a climb where you are generating plenty of your own heat. The deep venting half zip on the Pull-On is the tool here, and it is a real design decision rather than a token one. Drop the zip on the steep bit, close it at the top when the wind finds you. That is the fleece working as intended.

Under a shell, as the insulation in a system. When the weather turns, the Nexus goes under a waterproof or a windproof and does the insulation job while the shell does the wind and rain job. Because it breathes so well, it is a good citizen in that system: it will not turn your shell into a sauna the way a denser fleece can, and it dries out fast when the rain stops. The slim cut helps here too, since a shell slides over it without the bulk fight you get layering a lofted fleece.

What it does not want to be is your standing-around layer. Stop for lunch on an exposed top in a cold wind and the thin grid fabric gives up its warmth quickly, and the open structure lets wind rob it faster still. That is the moment you either keep a warmer layer in the pack or accept that this fleece is a moving-clothes fleece and dress accordingly.

Warmth-for-weight, honestly framed

The Nexus has a strong warmth-for-weight reputation and I think it is deserved, but the phrase gets misread all the time, so here is the honest version.

Warmth-for-weight means it delivers a lot of warmth per gram carried. It does not mean it is warm in absolute terms. Those are different claims. A 250g grid fleece punching above its weight is still a 250g grid fleece. As an active midlayer, where every gram you are not wearing matters and breathability keeps you from soaking through, that efficiency is exactly what you want. As a "keep me warm when I stop" fleece, the low absolute warmth is the ceiling, and no amount of clever grid gets you past it.

So I would not sell the Nexus to anyone who says the word "warm" first. If warmth is the priority, look at a high-loft piece instead: the Montane Protium with its Polartec Thermal Pro High Loft is the obvious step across, and Rab's own Superflux (covered in the roundup) does the warm-fleece job from the same brand. The Nexus is the one you buy when breathability comes first and warmth second.

Pull-On or Hoody

Rab sells the Nexus in two shapes and the choice is straightforward.

The Pull-On is the purer active piece. The half zip saves weight and gives you the deep venting collar-to-chest opening that a grid fleece really benefits from, and the single zipped chest pocket is enough for a phone or a snack. At around 250g it is the lighter, cleaner layering option, and for most hikers using it as a midlayer under a shell, it is the one I would point at first.

The Hoody adds a helmet-compatible hood, a full-length YKK VISLON zip and two zipped hand pockets, at around 308g. The hood is worth having if you want the fleece to work as a standalone outer more often, or you are layering it under a helmet for scrambling. You pay for it in a little weight and around a tenner more. If in doubt, and you mostly layer under a shell, save the weight and take the Pull-On.

Who it suits

The Nexus makes sense if:

• You are a high-output hiker who runs hot and keeps sweating out denser fleeces on the climbs
• You layer properly and want a breathable insulation piece to live under a shell in a system, not a do-everything jacket
• You want strong warmth-for-weight in a light, packable, fast-drying midlayer for moving in
• You want a piece with good sustainability credentials: mostly recycled, PFAS-free

It is the wrong buy if:

• You want a warm fleece to get cosy in at camp or standing around. Wrong category. Go high-loft
• You want one layer that handles wind and cold on its own. A grid fleece is thin and wind cuts through it. Pair it with a shell or buy a softshell
• You feel the cold and hike at a gentle pace, where a warmer fleece would serve you better than a breathable one

Honest limits

Nothing here is a knock on the Nexus, it is just being clear about a grid fleece so you buy the right tool.

It is thin, and it is not a standalone warm layer. Wind passes through the open grid quickly, so on exposed days it needs a shell to reach its potential. It is not windproof and does not pretend to be. And like most light stretchy grid fleeces, the face fabric is more prone to pilling and to snagging under pack straps over time than a hard-faced fleece is, which is the price of that soft, breathable build.

Judged as what it is, a light active midlayer for moving in, none of that counts against it. Judged as a warm fleece, all of it does, which is exactly why the framing at the top matters.

Pros and what to know

• Thermic G grid construction breathes and regulates well on the move
• Strong warmth-for-weight in a light, packable, fast-drying midlayer
• Deep venting half zip (Pull-On) is a real design decision for active use
• Slim regular cut layers cleanly under a shell without a bulk fight
• Good sustainability story: mostly recycled fabric, PFAS-free
• Sensible UK price, around £70 for the Pull-On

• It is a grid fleece, not a warm fleece: thin, and not for standing around in the cold
• Not windproof; the open grid needs a shell over it on exposed days
• Soft face fabric is more prone to pilling and pack-strap snagging than a hard-faced fleece
• Not a warm fleece: it is a breathable moving layer, not one for standing still in the cold

Verdict

The Rab Nexus deserves its UK following. As a lightweight grid midlayer it does the important things well: it breathes hard when you are working, it dries fast, it carries strong warmth-for-weight, and at around £70 for the Pull-On it is fairly priced for what it is. The grid construction is not marketing, it is the reason the fleece regulates the way it does, and Rab has tuned Thermic G squarely for moving in.

The only way to get this purchase wrong is to expect the wrong thing from it. This is an active midlayer, worn on the climbs or layered under a shell, and it is thin on purpose. If that is the job you are hiring for, the Nexus is one of the easiest fleeces in this cluster to recommend. If you actually want warmth, buy warmth: cross to the Montane Protium or Rab's own Superflux instead.

For a grid alternative with a different fabric and fit, the Mammut Aconcagua runs Polartec Power Stretch Pro in a slimmer Euro cut and is worth a look before you commit. And to see where the Nexus sits against the whole field, start with the best hiking fleeces roundup.

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