Castelli call it a light jacket but the comfort range is surprising. It dips well into temperatures where you might normally reach for a full protection jacket, yet the surprising breathability makes it still comfortable in temperatures when you may have worn arm warmers and a vest in the past. And it keeps you dry.
RoS stands for Rain or Shine. Its a label Castelli give their most advanced products that excel in both dry and wet conditions. For dry conditions, youre looking for comfort along with breathability to prevent you from getting wet and chilled from the inside. But with wet-weather clothing, youre looking for protection that will help you stay warm by keeping the rain out and letting sweat escape.
The Alpha RoS W Light Jacket ticks both of those boxes. Both the front and back materials represent a significant step forward in rain protection. These fabrics are used with reduced seaming, and seam sealing where necessary.
Castelli call this functional waterproofing because while they dont guarantee that no drop will ever enter the jacket, they promise that this is the best effort to keep you warm and dry in the widest range of conditions.