ThruDark Phalanx Fleece review: their best-known piece, judged as clothing

The Phalanx Fleece is the piece most people picture when they think of ThruDark, and as far as I can find, nobody has written an independent ThruDark Phalanx Fleece review. The brand's flagship shells get seeded to magazines. The fleece that has been in the range since 2019, their longest-serving design, has not. So this is that review.

I own one: black, non-hooded, size medium, bought at full retail price from ThruDark directly. No sample, no discount, no relationship with the brand.

The short version: this is a very well-made, very warm fleece built on the best fleece fabric Polartec produces, and it costs £240. Whether that is a fair exchange depends on what you expect a fleece to do, and on how honest you are with yourself about why you want this one. Both of those get a straight answer below.

If you want the full picture on the brand itself, the founders, the fabrics and how the range fits together, that is in the ThruDark brand review. This piece stays on the fleece.

Who the Phalanx is for

ThruDark was founded by two former Special Boat Service operators and runs its operation from Poole, about half an hour from where I hike. The military heritage is real and it shapes the styling: the hook-and-loop insignia patches on the sleeves, the muted colours, the name. None of that changes what the garment is, which is a high-loft fleece mid-layer.

It suits you if:

• You want a serious cold-weather mid-layer for hiking, and you layer properly (fleece under a shell, not fleece instead of a shell)
• You run cold, or you spend a lot of time stationary in the cold, where High Loft's warmth-to-weight advantage actually earns its keep
• You like the brand and want its best-known piece rather than a lookalike

It does not suit you if:

• You want one jacket that handles wind on its own. ThruDark's own product page rates the Phalanx 2 out of 10 for wind resistance, and they are right to
• You are shopping on price alone. This is a premium piece and it makes no attempt to be anything else
• You need something packable. High-loft fleece is bulky in a pack by nature; if compressibility is the priority, synthetic insulation is the right tool for that job

Specs

Price

£240

Body fabric

Polartec High Loft

Panels

Polartec Power Grid (underarm/side)

Zips

YKK throughout

Fit

Regular (ThruDark advise buying your usual size)

Cuffs and hem

Elasticated, with thumb loops

Pockets

Chest and hand pockets

Detailing

Hook-and-loop insignia patches on sleeves

Variants

Non-hooded, hooded and gilet; men's and women's

Made in

Portugal

Warranty

5 years, plus lifetime repairs

Brand's own ratings

Thermal 8/10, breathability 8/10, wind resistance 2/10, durability 6/10

Those last figures are worth pausing on. ThruDark publishes performance ratings on its own product pages, including the unflattering ones. A brand rating its best-known product 2 out of 10 for wind resistance and 6 out of 10 for durability is doing something most outdoor marketing departments would not allow. I will come back to both numbers.

The High Loft warmth story

Polartec High Loft is the top of Polartec's fleece line for warmth-to-weight. Polartec describes it as having the greatest warmth-to-weight ratio of all its fleece technologies, and Polartec itself features the Phalanx as a partner product, which tells you ThruDark is not buying seconds.

The way High Loft works is simple physics. Instead of the dense, flat pile of a standard fleece, the fibres are long and lofted, trapping a much thicker layer of still air for the same fabric weight. Air is the insulator; the fleece is just the scaffolding. The result is a fabric that feels almost absurdly soft and delivers more warmth per gram than the microfleece most of us grew up with.

ThruDark rates the Phalanx 8 out of 10 for thermal performance and that matches the fabric choice. This is a proper cold-weather mid-layer, not a spring windcheater.

The trade-off built into that lofted structure is the same thing that makes it warm: it is open. Which brings us to the two sections below.

Breathability and the layering role

The Phalanx is not one uniform fabric. The underarm and side panels are Polartec Power Grid, a thinner grid-backed fleece designed to move moisture and stretch with you, and the body uses open mesh stitching that vents excess heat when you are working hard. ThruDark rates breathability at 8 out of 10, and the construction backs the number: the warm fabric sits where you need warmth, and the dumping-heat fabric sits where you sweat.

That construction tells you exactly what this garment thinks it is. It is a mid-layer. It is designed to sit under a shell on cold days, breathe well enough that you do not soak your baselayer on the climbs, and hold warmth when you stop. Used that way, with a waterproof like my Patagonia Torrentshell over the top when the weather turns, the system works exactly as intended.

It also works as a standalone outer on calm, dry, cold days: the frosty still morning, the walk from the car park, the campsite evening. High Loft on its own in those conditions is lovely. The moment the wind gets up, it stops being an outer layer, and that is not a flaw so much as a category fact.

The wind resistance truth

ThruDark rates the Phalanx 2 out of 10 for wind resistance. Their number, on their own product page, about their best-known product.

I want to be clear about what that means, because it is the single most important thing to understand before spending £240. A lofted fleece is essentially a wearable air trap with no barrier layer. Wind blows straight through the pile and strips the warm air out, and the warmer the fleece feels indoors, the more dramatic the difference feels when a gust removes all of it at once. On an exposed coastal ridge in a stiff breeze, an unshelled Phalanx will feel colder than a much thinner windproof layer.

So the honest framing is this. The Phalanx is brilliant when:

• It is under a shell in cold, wet or windy conditions, doing the insulation job while the shell does the wind job
• The air is cold and still, where its warmth-to-weight is at its best
• You are in and out of activity and need something that breathes on the move and insulates at rest

And it is the wrong tool when:

• You want a single outer layer for exposed, windy UK hill days. Anywhere I hike, the Purbecks, the coast path, the Beacons, wind is the default, not the exception
• You are choosing between this and a windproof softshell for one do-everything jacket. Buy the softshell

None of this is a criticism of the Phalanx. It is a criticism of buying a high-loft fleece and expecting it to be a shell. Credit to ThruDark for printing the 2/10 rather than hiding it.

Build quality

This is where the £240 starts to show up in ways you can point at.

The zips are YKK throughout, which is the correct answer and not a given at any price. The cuffs and hem are elasticated, and the cuffs carry thumb loops, which matter more on a mid-layer than people think: they hold the sleeve in place while you pull a shell over the top, so the fleece does not bunch at your elbows. The chest and hand pockets cover the basics.

The insignia patches on the sleeves are hook-and-loop, so you can run the ThruDark patches, swap in your own, or leave the fields blank if the look is not for you. This is the most obviously military-derived detail on the garment and the easiest to ignore if you want to.

It is made in Portugal, which puts it in the same manufacturing tier as a lot of premium European outdoor kit, and it carries a 5-year warranty with lifetime repairs behind it. That warranty is a meaningful part of the value case at this price.

One number to keep in view: ThruDark's own durability rating is 6 out of 10. High-loft fabrics pill and flatten faster under pack straps and repeated abrasion than hard-faced fleeces do; that is inherent to the fabric type, not a ThruDark defect. If you hike with a heavy pack over a fleece day in, day out, expect the shoulders to show it eventually on any high-loft garment.

Fit and sizing

ThruDark describes the fit as regular, neither athletic nor loose, and advises buying your usual size. Their model data supports that: the medium is shown on a 178cm, 83kg model, which is about as standard a UK medium as it gets.

I bought a medium, my usual size.

Two practical notes. First, a high-loft fleece is bulkier than a grid fleece or microfleece of the same warmth, so check your shell has room for it; a trim-cut waterproof over a lofted medium can feel tight across the shoulders. Second, the thumb loops set an effective minimum sleeve length, so if you are between sizes and normally size down for sleeve fit, try before committing.

The £240 question

£240 is a premium price, so here is exactly what it buys, as plainly as I can put it.

The fabric. Polartec High Loft is the warmest fleece fabric Polartec makes, and Polartec is happy to put its own name next to this garment. The loft is what you feel the moment you put it on: it traps more air than a standard fleece, which is where the warmth-to-weight comes from. The mapped Power Grid underarm panels are the clever part, dumping heat exactly where you generate it so the fleece stays usable on the move rather than only at rest.

The construction. YKK zips, thumb loops that actually stay put, hook-and-loop insignia patches, and Portuguese manufacture. Up close the build quality is visible: clean seams, dense stitching, hardware that operates like it will still operate in year five. The 5-year warranty and lifetime repair service back that impression with something contractual.

The brand. Part of what you are buying is ThruDark: the founders' story, the Poole operation, the patches, the fact that this is the piece the brand is known for. That is how premium kit works, and in ThruDark's case the story underneath the price is verifiably real. The garment carrying it is properly made and uses a fabric that earns its premium position.

What you are not getting for £240, and should not expect, because the brand tells you so itself: windproofing, packability, or a do-everything outer layer. It is a cold-weather mid-layer, and judged as one, it is excellent.

Pros and what to know

• Polartec High Loft body, the warmest fleece fabric Polartec makes, with the warmth-to-weight to match
• Smart construction: Power Grid underarm panels and vented stitching keep it usable on the move
• YKK zips, thumb loops and Portuguese manufacture; the build quality is visible up close
• 5-year warranty plus lifetime repairs
• The brand publishes its own unflattering ratings, and the product matches its honest billing

• £240 is a premium price: be sure a cold-weather high-loft mid-layer is the job you need filling
• Wind resistance is 2/10 by ThruDark's own rating: this needs a shell in typical UK hill weather
• High-loft fabric is bulkier than grid fleece and vulnerable to pack-strap abrasion over time
• The military styling and insignia patches will not be to everyone's taste, even if removable

Verdict

The Phalanx Fleece is a good garment with an honest spec sheet. As a piece of clothing it does exactly what a high-loft fleece should: excellent warmth for the weight, real breathability from the panel construction, quality hardware, and a fabric that Polartec is happy to put its own name beside. As a purchase it is a premium buy that delivers a premium garment, and it makes the most sense when the brand is part of what you are buying, which for most people considering it, it is.

I bought one knowing that. If you have read this far and the 2/10 wind rating has not put you off, you already understand what this fleece is for, and it does that job very well.

Next in this series: the Black Ops Dyneema Jumper review, where I ask whether Dyneema in a cotton sweatshirt means anything. And for the whole picture on the brand, start with the ThruDark brand review.

FAQ