Castelli seeks to combine aerodynamics with perfect fit and comfort, and that's why the Climber's 4. 0 Limited Edition Jersey is designed to be a lightweight aero jersey that will excel at dealing with the rigors of road racing in the heat and high in the mountains. It sees maximum aerodynamics with the Flusso 3D front-facing fabric, an Airflow shoulder construction, and StradaPro 3D rear-facing fabric for added breathability and airflow. Even if we're not a pro racer, we appreciate the quick-drying and sun-blocking properties of the Climber's 4. 0, not to mention the additional airflow for when the sun's beating down and we're still miles out at the end of an arduous stretch of riding.