Castelli's Perfetto RoS 3: How Polartec AirCore Redefines "Breathable"

For decades, performance cycling apparel has faced a fundamental paradox: how to keep rain out without trapping performance-sapping sweat in. Cyclists know the feeling all too well—a "waterproof" jacket that leaves you just as wet from internal condensation as you would have been from the rain. Castelli, a brand synonymous with innovation, is now claiming to have solved this puzzle with its new Perfetto RoS 3 Jacket, powered by a genuinely revolutionary fabric called Polartec® AirCore™.

This isn't just another incremental update. Castelli is positioning the Perfetto RoS 3 as the start of a new era in cycling apparel, one where staying dry from the inside out is the new gold standard.

Steve Smith, Head of Cycling at MVC Group, puts it bluntly: “It’s hard to fully explain how revolutionary this fabric is. 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.”

So, what is this groundbreaking technology, and how does it work?

The Science of AirCore™: Harnessing Air to Keep You Dry

The magic behind the Perfetto RoS 3 lies in its exclusive Polartec® AirCore™ fabric. To create its unique membrane, a hydrophobic polymer is subjected to 20,000 volts and forced through a tiny needle. This electrospinning process creates a web of microscopic filaments—roughly 100 times smaller than a human hair—that form a barrier with incredible properties.

A New Definition of Breathability Unlike traditional membranes that act as a passive wall, AirCore™ is engineered to be actively breathable. It's "essentially windproof," a term used deliberately by Castelli. The fabric allows a very small, imperceptible amount of air to pass through. This controlled airflow is the key: it picks up sweat vapor from your skin and actively transports it outside the jacket, creating a stable microclimate that keeps you dramatically drier during hard efforts.

Functional Waterproofing AirCore™ is also "essentially waterproof." While some brands chase massive hydrostatic pressure ratings, Castelli and Polartec® took a more practical approach. A fabric is often defined as "waterproof" if it can withstand a 10,000mm column of water. However, real-world rain exerts a pressure of only around 800mm. AirCore™ boasts a rating of 5,000mm, meaning it can handle over six times the force of normal rainfall. It’s functionally waterproof for the vast majority of conditions a cyclist will ever face, without the clammy feel of a full-on rain slicker.

Unprecedented Comfort and Stretch The electrospun membrane can stretch to over twice its original size, allowing the Perfetto RoS 3 to offer an incredibly comfortable, non-restrictive fit that adapts to your body shape on the bike.

Industry-Leading Sustainability

Perhaps most impressively, this leap in performance is matched by a commitment to sustainability. AirCore™ is 100% PFAS-free and is constructed from recycled polyester yarns. While making a PFAS-free fabric waterproof is relatively simple, achieving elite-level breathability at the same time has been the industry's greatest challenge. AirCore™ delivers on both fronts, setting a new benchmark for eco-conscious performance.

The Perfetto RoS 3 Jacket in Detail

Built for cool-to-cold conditions ranging from 4−14°C (39−57°F), the jacket is more than just a revolutionary fabric. Castelli has applied its signature attention to detail throughout:

• Taped Shoulder Seams: Reflective taping provides extra rain protection in a critical area.
• Targeted Ventilation: Zippered vents on the chest allow for customized airflow.
• Premium Zipper: A two-way YKK® Vislon® zipper allows for easy adjustment from the top or bottom.
• Practical Storage: Three rear pockets feature laser-cut drain holes to prevent water from pooling.
• Full Coverage: A longer, dropped tail protects from wheel spray, while a high collar seals out drafts.

The Takeaway

With the Perfetto RoS 3 Jacket, Castelli isn't just selling another piece of clothing; it's presenting a new philosophy for performance apparel. By prioritizing active breathability over absolute waterproofness, it promises to keep riders more comfortable—and therefore performing better—in the widest possible range of "Rain or Shine" conditions.

For cyclists tired of choosing between getting wet from the outside or the inside, this jacket may truly be the perfect solution.

The Castelli Perfetto RoS 3 is available now for men and women with a suggested retail price of $320.00 / €249,95 / £280.00. Castelli and its sister company Sportful have exclusive rights to AirCore™ in cycling until fall/winter 2026.