In the past year, we've seen Castelli do something unusual, yet welcomed -- making winter versions of our favorite summer-weight jerseys. And the latest in this line of adaptable jerseys is the Aero Long Sleeve Jersey. Featuring the same cut and aerodynamic properties of the Aero jersey, the Aero Long Sleeve uses breathable, warming fabrics to make it the ideal cool weather jersey.It seems like a simple idea -- take your most aerodynamic jersey and add some thermal stuff to it. Not the case for Castelli. Retaining both the shape and aero properties, while using weightier fabrics, required a thoughtful approach. First, and most obvious, the materials need to provide warmth. However, they also need to be resilient to cold winds without throttling breathability. What fabric encompasses all of these characteristics and still has race-day aerodynamics? Thermoflex Lite. This material has an incredible amount of stretch to eliminate the folds and bunching that disrupt airflow over the jersey. Its tight weave also makes the front of the jersey resistant to wind. So, you'll be aerodynamically slippery while shielding yourself from icy chills. To deal with general, atmospheric cold, the inner-lining features a high loft that warms while pulling moisture away from the skin. And aside from this, the fabric is extremely soft as to eliminate the threat of abrasion.For the rear of the jersey, Castelli used its Warmer material to promote a heightened level of breathability and structure. In conjunction with the rear hem's silicone gripper, the jersey retains its shape and fit when the three rear pockets are loaded up with your ride essentials. Castelli has also added reflective elements throughout the jersey for added visibility in low-light conditions.The Castelli Aero Long Sleeve Jersey is available in six sizes from Small to XXX-Large and in the colors Black/white and Red/black.