Castelli Cold Days W 2nd Layer

Additional insulation, longer-lasting warmth.

The Polartec® Alpha® material is an excellent heat retainer; it is also soft, elastic, and lightweight. A few years ago, we thought this material would be great for base layers, but it felt damp and clammy against the skin. However, when we were looking for additional insulation for rides on gravel in sub-zero temperatures, we tried the Alpha® prototypes as a second layer over a Prosecco base layer—and discovered the best combination for cold-weather rides. We refined the details and developed this second layer specifically for cold-weather outings. We chose a half-zip design to avoid bulk at the lower part of the jacket, and positioned the zipper slightly off-center to prevent multiple zippers from overlapping at the neck. We focused on a close fit, allowing you to decide whether to tuck the shirt into your pants or wear it over, as we do. Additionally, we found that it pairs well over a base layer from the Flanders, Bandito, Miracolo, or Seamless models.

Technical specifications

• Polartec® Alpha® 90 – high-loft functional insulation material made from recycled PET
• Maximum breathability
• Asymmetrical zipper
• High collar.