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DEEP Collection, the new definition of a running T-shirt

by Paco Amorós

42K Products

At 42K, we’ve spent years driving textile innovation as the force behind continuously improving our technical apparel collections. We listen to runners, test fabrics, develop patterns, and challenge ourselves to raise the bar with every new running T-shirt collection we launch.

That’s how DEEP was born: a collection designed to take performance one step further, with brand-new details in our catalogue and a blend of design, technology and comfort that makes it our most advanced option yet for demanding training sessions and races.

DEEP Collection with laser micro-perforations. — Athletes Soukaina El Khayami and Kike Ríos wearing the DEEP Dark Blue model.

DEEP Collection, with two-way stretch and laser micro-perforations

DEEP reflects 42K’s determination to keep running towards the future and set the pace for technical innovation in the running world. This new collection of short-sleeve T-shirts, designed specifically for running, is a step forward in performance, comfort and design thanks to two technical innovations: a fabric with two-way stretch that ensures a greater range of motion, plus an area of laser micro-perforations to guarantee excellent breathability.

The DEEP collection features a relaxed fit pattern (relaxed fit) that delivers excellent anatomical comfort for athletes who push themselves to the limit in training and competition.

Elastter, unrestricted freedom of movement

At the heart of the DEEP collection is Elastter, the most advanced technical fabric 42K has developed to date. It’s a blend of 88% recycled polyester and 12% spandex/elastane (a fibre known for its ability to stretch and return to its original shape without deforming), resulting in an ultralight material with excellent adaptability and outstanding technical performance.

DEEP Collection with two-way stretch — The DEEP collection is made with Elastter fabric, known for its two-way stretch.

Elastter offers two-way stretch that lets the fabric follow the body’s natural movement without resistance. This ability to stretch in two directions ensures total freedom with every stride, every turn on the route, every change of pace. Whether it’s a long run or a short high-intensity interval, the fabric adapts effortlessly to the athlete’s body, reducing friction and improving overall comfort.

But what defines Elastter, beyond its flexibility, is its extraordinary softness to the touch. The fabric feels light and silky on the skin, delivering a second-skin sensation that makes a difference in longer sessions. This softness adds comfort and also helps prevent chafing, even in high humidity or heat.

DEEP T-shirts, thanks to Elastter fabric, deliver a feeling of total freedom, fluidity and lightness, making for a more natural and comfortable running technique. If you want to learn more about Elastter fabric, here’s a detailed article: “Elastter, 42K’s new premium fabric”.

We can say, without fear of letting any runner down, that the DEEP collection offers total freedom of movement, with no restrictions, thanks to the combination of Elastter fabric and the relaxed fit cut.

DEEP is the second T-shirt collection in the 42K catalogue to use this next-generation fabric; the APEX tank top collection was the first to debut Elastter and has already become a bestseller. If you want to check out every APEX model, they’re available in our online shop: APEX collection.

Laser micro-perforations, innovation to improve breathability

The big technical innovation in the DEEP collection is the laser-made micro-perforation zones, strategically placed on the sides of the front of the T-shirt.

This detail, which represents a major leap forward in 42K’s textile manufacturing technology, significantly improves the breathability of DEEP T-shirts. The micro-perforations increase ventilation capacity right where the body needs it most during a run, supporting thermal regulation and delivering a continuous feeling of freshness.

Thanks to this innovation, the DEEP collection becomes an ideal choice for demanding training sessions in high temperatures and for races in the summer months when heat becomes yet another opponent for the athlete. The combination of an ultralight, breathable fabric with an additional ventilation system makes these T-shirts essential allies for running without limits, even on the hottest days of the year.

A collection inspired by the sea

The name DEEP is inspired by the depths of the ocean—its apparent calm, its inner energy, and its extraordinary biodiversity. That connection to the marine world is reflected in the colour palette chosen for the three models in the collection:

DEEP Dark Blue: understated elegance with dark blue tones—refined and intense—that evoke the depths of the deepest waters and convey calm and determination.

DEEP Mint: visual freshness for those looking for a more vibrant, modern design, with aqua tones reminiscent of the light that filters through tropical reefs.

DEEP White: a clean, minimalist option inspired by the delicate whiteness of corals.

Each model is available with a specific pattern for men and women, adapting the fit to each type of athlete’s body. The relaxed fit cut (relaxed fit), combined with the fabric’s stretch, ensures a fit that’s both comfortable and technical, supporting unrestricted movement without discomfort.

Safety in motion: rear reflective detail

We know many runners train early in the day or at dusk, especially in the hottest months of the year to avoid high temperatures, when visibility can be limited.

DEEP T-shirts include a small reflective strip on the back, which acts as an extra visibility element in low-light conditions. This simple but important addition boosts safety without changing the garment’s clean, sophisticated design.

DEEP Collection with a reflective strip on the back. — The DEEP collection features a reflective strip on the back.

Technology in the service of performance

In addition to its next-generation fabric and the inclusion of laser micro-perforations, DEEP T-shirts feature the three most advanced technologies in our catalogue to guarantee maximum performance during use:

Soft-Light: this technology ensures a soft, delicate feel, preventing chafing even during long sessions or in adverse weather conditions.
Dry-Tec+: a quick-dry system that speeds up sweat evaporation and helps keep skin dry and body temperature regulated.
DC4 – Long Life Run: a special treatment to ensure high colour durability, even after multiple washes and intensive use.

A proposal designed for high performance… and much more

DEEP isn’t just a technically flawless collection; it also represents an aesthetic evolution within the 42K catalogue. The colour palette, sublimated designs and the reflective strip on the back make each T-shirt stand out in style too, without sacrificing functionality.

This collection is designed for demanding runners who want performance without giving up comfort or design. But it’s also a perfect option for regular training, mid- and long-distance races, or even for functional activities outdoors or indoors where freedom of movement and ventilation are crucial.

DEEP Collection with ultralight, soft fabric. — Athletes wearing the White model from the DEEP collection.

Commitment to sustainability

At 42K, we continue to strengthen our commitment to more responsible production. That’s why the Elastter fabric used to make the DEEP collection uses 88% recycled polyester, helping reduce environmental impact without sacrificing technical performance. We believe innovation shouldn’t be at odds with environmental commitment, and DEEP is a clear example of that.

“We’re especially proud to present the DEEP collection, not only for its technological innovation and design, but because it represents everything we want to offer as a brand: sustainable garments with high technical performance, designed to support athletes in their most demanding challenges. DEEP is, without a doubt, a step forward for 42K”, explains Guillermo Peñalver, 42K’s manager.

42K’s commitment to sustainability is unequivocal, which is why since 2019 we’ve been working on developing technical fabrics that are fully recycled or have a high recycled content. Infini_Tech was our first 100% recycled fabric, made with polyester yarn obtained from recycled plastic bottles, and it has brought to life several highly successful collections such as Elements, Ozone, Wave and Pangea. We also have TriActive, also 100% recycled, used to make the Motion collection.

DEEP represents a new era for 42K technical running T-shirts. A collection born from hard work, active listening and research, ready to go with you where the real effort begins: in every kilometre still to come.