Castelli has released a new Perfetto RoS 3 jacket that it claims “revolutionises breathable protection” thanks to an entirely new fabric – free from PFAS-based chemicals – developed with Polartec. This AirCore fabric is exclusive to Castelli and its stablemate Sportful in the cycling world, although the developers believe it will have a huge impact across the outdoor clothing market generally.
2025 Castelli Perfetto RoS 3 Jacket.jpg (credit: road.cc)
Polartec AirCore is all about breathability. At least, that’s the starting point of this whole thing. Breathability with windproofing and water repellency. And Castelli reckons it sets new standards.
Okay, so when you’re out cycling, you know that you can get wet from outside – rain and road spray – and from sweat. Different sources, but pretty much the same result: you become uncomfortable. That’s what AirCore is intended to avoid.
“AirCore has been engineered to keep cyclists dry from the inside out,” says Castelli.
“Instead of just blocking rain, the Perfetto RoS 3 Jacket’s AirCore construction takes a more intelligent approach. It actively ventilates sweat away from riders’ bodies using the natural power of airflow, creating a microclimate that keeps the core stable and performance high, even during the most intense rides.”
2025 Castelli Perfetto RoS 3 jacket Polartec AirCore taped shoulder (credit: Castelli)
That certainly sounds interesting. Steve Smith, head of cycling at MVC Group (home to Castelli and Sportful), goes further.
“It’s hard to fully explain how revolutionary this fabric is,” he says. “Its properties achieve something that’s never been done before, which is why we’re re-writing the gold standard of what high-performance cycling gear can do. No one else is anywhere close.”
That’s fighting talk, so what’s going on here?
Castelli argues that most cyclists don’t spend a whole lot of time riding in pouring rain (even in the notoriously wet UK), so it’s sweat that’s the greater enemy. Making a fabric waterproof is relatively straightforward – a polythene bag will keep water out – but making it breathable, especially without PFAS, is difficult.
“The unique combination of air permeability and Polartec’s nano-fibre membrane lets Polartec AirCore keep you dry while still maintaining the windproof and water repellency of the fabric,” says Castelli.
2025 Castelli Perfetto RoS 3 jacket Polartec AirCore action (credit: Castelli)
“This state-of-the-art technology leverages air to maintain a dry microclimate by evaporating sweat from the outside in. Which, when you think about it, is the primary warmth management mechanism that truly matters for an active user. The harder you work, the harder the fabric works. Motion fuels ventilation that carries moisture away from the body. By staying drier and more comfortable, users can experience air-powered, permeable, enhanced performance.”
How does it work?
“AirCore is essentially windproof, and it is that ‘essentially’ part that makes this [Perfetto RoS] jacket so special,” says Castelli. “It has been engineered to let in a very small, imperceptible amount of air that picks up sweat moisture and carries it outside the garment, ensuring that riders stay drier than they ever thought possible with a membrane jacket.”
If you want to put figures on it, Polartec says that AirCore delivers air permeability of 0.7 cubic feet per minute (CFM), whereas most competitor fabrics have no air permeability. It also offers a moisture vapour transmission rate (MVTR) of 35,000 g/m²/24 hour, although Polartec says that this metric “has very little correlation to real life” because it doesn’t take air permeability into account.
2025 Castelli Perfetto RoS 3 Jacket – Rossa Corsa logo.jpg (credit: road.cc)
What about stopping rain and spray from getting in, though? Castelli describes AirCore as “essentially waterproof”.
Why that terminology? If a jacket is described as having a 20,000mm hydrostatic head rating, that means that a 20m-high column of water can stand on the fabric without that water getting through. In some countries, a fabric must achieve a hydrostatic pressure test score of 10,000mm to be defined as waterproof.
Castelli says, “However, rain only falls with a hydrostatic pressure of around 800mm, so the 5,000mm test score AirCore achieves means normal rain would have to fall with 6.25 times more force than it usually does to permeate the fabric. That means AirCore is functionally waterproof, allowing riders to stay drier in the widest range of conditions.”
In other words, Castelli is saying that AirCore keeps water out as well as it needs to for most circumstances, while prioritising breathability. The fabric is also free from PFAS-based chemicals and made from recycled polyester. PFAS (per- and polyfluoroalkyl substances) are often called “forever chemicals” due to their inability to break down naturally.
> How green is your waterproof cycling jacket?
“The membrane is produced by a process called electrospinning, where a hydrophobic proprietary polymer is pushed through a hypodermic needle charged at 20,000 volts,” says Castelli. “Under pressure, it emits a thin jet of microscopic filaments – approximately 100 times smaller than a human hair – which falls like snow to create an incredibly tight membrane that still allows air to permeate it.”
Steve Smith says: “Traditionally, there has always been a compromise between breathability and water protection. We bucked the industry trend by refusing to choose one over the other. By speaking to a range of fabric suppliers, engineers, and scientists from around the world, we found in Polartec a brand that truly understood what we were trying to achieve.
“What we’ve delivered with Polartec on the AirCore project has far exceeded what we ever thought possible. Not only have we developed a fabric that is off-the-charts in terms of breathability, it is also highly water repellent, lightweight and windproof, as well as being incredibly stretchy and comfortable.”
AirCore is stretchy too. The membrane can be extended to over twice its original size. The idea, of course, is that it can adapt to your shape and keep you comfortable (you can head over to Polartec’s website for more details on the tech behind AirCore).
The Castelli Perfetto RoS 3 is the first item of clothing to feature the new fabric. It is designed to perform in both wet and dry conditions, and in a 4-14°C temperature range.
2025 Castelli Perfetto RoS 3 jacket Polartec AirCore zip open studio (credit: Castelli)
The high collar is intended to keep out draughts, and the rear is dropped for coverage from wheel spray. Although most of the seams aren’t taped, you do get reflective external taping around the shoulders.
2025 Castelli Perfetto RoS 3 Jacket – pockets.jpg (credit: road.cc)
There’s more reflective detailing at the bottom of the pockets.
2025 Castelli Perfetto RoS 3 jacket Polartec AirCore zipped side vent (credit: Castelli)
The YKK Vislon front zipper is two-way, and there are zipped vents on the sides of the chest.
The Castelli Perfetto RoS 3 is available in both men’s and women’s cuts and in various colours, priced at £280. More AirCore will be released in the coming weeks and months.
The Castelli Perfetto RoS 3 has already arrived here at road.cc, so stay tuned for a review.