ThruDark Oryon Delta Long Sleeve T-Shirt review: a highly breathable base layer boasting advanced fabric tech

We hit the heights in ThruDark’s Oryon Delta Long Sleeve T-Shirt, a premium base layer featuring Polartec’s innovative Delta fabric

ThruDark Oryon Delta long-sleeved t-shirt: hiking in Snowdonia
(Image: © Alex Foxfield)

Advnture Verdict

An excellent t-shirt for outdoor activities, the Oryon is comfortable and performs beautifully in the backcountry. Polartec’s breathable Delta fabric works wonders, making this a superb standalone layer for hot weather hikes and I found it to be a great shout as a base layer in cold conditions too.


  • +

    Highly breathable

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    Odor minimizing fabric

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    Long front zip for dumping heat

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    Very comfortable

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    Good fit

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    Made in Ukraine


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    Zippered pockets perhaps unnecessary

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    Pricey compared to most base layers

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ThruDark Oryon Delta Long Sleeve T-Shirt: first impressions

ThruDark is a British brand whose founders were members of the United Kingdom’s Special Forces. Their experience of extreme climates and challenging situations has lead them to create an uncompromising product range, with everything from flannel shirts and caps to high performance outdoor apparel.

Don’t expect bright flamboyant designs – ThruDark’s kit is unapologetically macho in terms of aesthetic, with metallic color schemes, the occasional skull and the ever-present trident logo, hinting at a sort of mythical strength and power. Employing quality components, fabrics and materials, their clothing is designed to ‘endeavour through adversity’.

ThruDark Oryon Delta long-sleeved t-shirt: ThruDark's trident insignia

ThruDark's trident insignia emblazoned on Polartec's Delta fabric (Image credit: Alex Foxfield)

Its Oryon base layers, available as either short- or long-sleeved, make use of Polartec’s high breathable Delta fabric, which is designed to keep the wearer cool during activity in hot climes. The fabric is enhanced with Polartec’s Fresh Face, a natural and biodegradable odor reducer that’s a more sustainable alternative to traditional fabric fresheners.

I was keen to see how ThruDark's design and Polartec's innovative fabric fared when faced with the mountainous backcountry and was delighted to get the opportunity to find out earlier this year.

The Oryon (available to buy direct from ThurDark) looks and feels premium, with little design touches, such as the understated trident insignia on the left breast and below the collar or the small Union Jack flag tab – a touch that'll undoubtedly please patriotic Brits. To wear, the top's textured fabric is soft and feels pleasant against the skin.

With a list price of $140 (£110 in the UK), it’s more expensive than most hiking tops, though some merino options will set you back more. Nevertheless, I could immediately tell this was no bog-standard base layer.


RRP: $140 (US) / £110 (UK)
Weight: 250g / 8.8oz
Fabric: Polartec Delta
Sizes: XS to 3XL
Fit: Athletic
Colors: Green, Wolf Grey, Sand, Obsidian Black
Compatibility: Versatile base layer that can be worn for a range of adventurous activities

The main plus points of Polartec's Delta fabric are its moisture-wicking and fast-drying capabilities, along with what Polartec call its ‘metabolic cooling’ qualities. These benefits are achieved thanks to a combination of hydrophobic (water repelling) and hydrophilic (water absorbing) fibers. Turn the t-shirt inside out and look closely and you’ll notice a matrix of touch-points, which sit against the skin, ever so slightly raising the majority of the fabric.

ThruDark Oryon Delta Long Sleeve T Shirt: having a drink

The main benefits of Polartec's Delta fabric are its moisture-wicking and fast-drying qualities (Image credit: Alex Foxfield)

The fibers work with your sweat by first drawing perspiration away and then distributing it, holding moisture close to the skin. Hot air flowing through the trapped moisture is cooled, enhancing your body’s natural cooling system. This design has numerous advantages: it increases ventilation, allows for faster moisture dispersal and also avoids that clingy sensation that often occurs when working up a sweat.

As well as Delta’s cooling properties, the fabric is also treated with Polartec’s Fresh Face, a biodegradable, plant-based odor reducer. When launched earlier in 2023, the Oryon was one of the first products in the world to feature this innovation, along with 66 North’s Grettir tops. Derived from non-GMO mint oil plant extract, Fresh Face was tested comprehensively against traditional, metal-based additives over 50 wash cycles and was found to more than hold its own. In short, it means the Oryon not only repels unpleasant odors but is also kinder to the environment.

ThruDark Oryon Delta Long Sleeve T-Shirt: hiking in the Rhinogydd

The Oryon is wonderfully comfortable for long hiking days (Image credit: Alex Foxfield)

Two relatively large, zippered chest pockets give interesting storage options. I’m not overly convinced by them, both from a practical and an aesthetic point of view. Due to the thinness of the fabric, it’s a little uncomfortable putting anything at all substantial in there. I also think that the short-sleeved version of the Oryon, which doesn’t have pockets, looks all the better for it. Though beauty is obviously in the eye of the beholder, so you'd be within your rights to disagree.

The pockets are also mesh-lined on the inside, creating two layers, which are obviously less breathable than one. Benefits of the Delta fabric’s touch-point design are also wasted on the inside of the pocket, rather than being used against the skin below the pockets. On the plus side, the mesh is breathable. I also get the sense I’m nit-picking a tad here, which is what us reviewers end up doing when there's very little else wrong with a garment.

ThruDark Oryon Delta Long Sleeve T Shirt: pockets

The Oryon has two zippered chest pockets (Image credit: Alex Foxfield)

Interestingly, the apparel in the Oryon range, along with ThruDark’s Rōnin range, are made in Ukraine. ThruDark say that ‘every garment produced is a testament to the dedication of those continuing to endeavour in the face of such great adversity afflicting their homeland.’ This approach is certainly laudable.

ThruDark Oryon Delta Long Sleeve T-Shirt: on the trails

I put the Oryon to the test on strenuous hikes in Bannau Brycheiniog (the Brecon Beacons), Eryri (Snowdonia) and the Lake District national parks, with some pretty adverse weather conditions thrown in. For the entire stint in the Lake District, it remained firmly as a base layer, hidden beneath a fleece and waterproof outer.

I found it to be wonderfully comfortable as both a base layer or as a standalone on warmer days. It’s not as soft as a bamboo top, though its textured inner fabric feels lovely against the skin and it doesn't suffer from the slight itchiness of a Merino base. It’s also neither clingy nor baggy, with a nice fit that worked well under additional layers. I can also report that the Fresh Face odor-reducing treatment was effective, even after multiple wears and wash cycles.

The front half-zip came into its own on long ascents, allowing me to dump heat effectively when required. On such ascents, lesser base layers tend to cling when working up a sweat. Not so the Oryon, underlining the clever design of the Polartec Delta fabric’s touch-points.

ThruDark Oryon Delta Long Sleeve T-Shirt: in Y Bannau

Walking in the Bannau Brycheiniog National Park (Image credit: Alex Foxfield)

As well as this, I really liked wearing it in cooler climes too. It seems to insulate well in dry conditions, trapping warm air between between my body and the fabric, while its long sleeves make it a good shout for wintry adventures. It doesn’t have thumb loops, but the tight-ish fit of the arms meant that I never noticed it riding up when I added a mid-layer.

This wasn't the first collaboration between ThruDark and Polartec that I've tested for Advnture. I had an issue with the placement and heftiness of some of the seams on ThruDark’s Centurion Alpine Jacket but I’m glad to say I had no such qualms with the subtle seams on the Oryon.

All in all, this is a great base layer that's hard to pick fault with and one that I'll continue reaching for throughout the seasons.

Alex Foxfield

Alex is a freelance adventure writer and mountain leader with an insatiable passion for the mountains. A Cumbrian born and bred, his native English Lake District has a special place in his heart, though he is at least equally happy in North Wales, the Scottish Highlands or the European Alps. Through his hiking, mountaineering, climbing and trail running adventures, Alex aims to inspire others to get outdoors. He's the former President of the London Mountaineering Club, is training to become a winter mountain leader, looking to finally finish bagging all the Wainwright fells of the Lake District and is always keen to head to the 4,000-meter peaks of the Alps.