When Castelli designed the first aero jersey for road racing in 2006, everyone thought we were crazy, even some pro riders. Back then, aerodynamics was reserved for time trials. Performance clothing meant moisture management. And you could win the Tour de France in a baggy jersey that was little more than a polyester T-shirt with pockets on the back. Even our aero consultants expected little to no gains, so we called it the Split Second jersey. In the end, the gains were significant, and we completely revolutionized the look of the pro rider. We’re now on version seven of this jersey, and we’ve seen even more progress. Still relying heavily on CF riding position wake analysis for fabric and seam placement, as well as feedback from pro riders, this jersey is both fast and comfortable for long days spent riding. On race days, wear our Bolero SS Base Layer underneath the jersey for even more aerodynamics.