What The Perfect Winter Cycling Jacket Should Be
Castelli started with a list of things they didn't like about current jackets and set out to solve them and in the process they made their best jacket ever.
The first issue to resolve was related to moisture management. Even the best of the currently available fabrics provide a good level of breathability but can't keep up with the sweat generated during high-intensity riding.
So they invented a double-layer construction that allows you to open an outer wind-protection layer while keeping the insulation layer closed and thereby allowing airflow inside the jacket to evacuate moisture while avoiding direct contact with the skin.
On a long climb, you can unzip the outer layer to allow moisture to escape, and when the descent starts, you close the outer layer and are completely dry inside. It works so well that sometimes it feels like magic.
Next they focused on the openings: neck, waist, and, most of all, wrists.
The neck comes up high and is shaped to move with you, whether you're standing or in an aero position being a January hero and attacking your mates. For the waist they created a stretch layer with a silicone bead that lies flat and completely seals out wind without bunching or riding up.
At the wrists, you'll find a double-layer wrist opening: the inner layer lies under your glove and holds tight to your wrist, while the outer layer sits over your glove so that any rain will roll down the outside of the glove and not end up inside.
To ensure the Alpha RoS 2 holds up well in wet conditions, Castelli employed GORE-TEX INFINIUM™ WINDSTOPPER® fabric along with waterproof seam taping on critical seams around the shoulder. Other seams are hidden out of direct water flow, and the water-repellent treatment on the fabric is sufficient to prevent most moisture from entering. They call it essentially waterproof, using their own subjective judgment to strike a balance between water protection, breathability, and comfort. It doesn't mean that no drop will ever come in, but if you do longish rides in real rain, you will stay dry.
With a fresh update in its third generation, this jacket leads the way in demonstrating how a winter jacket should perform.