When Castelli engineered the first aero jersey for road racing back in 2006, everyone thought we were crazy. Back then, aero was only for TTs. Performance clothing meant moisture management. And you could win the Tour de France with a baggy jersey that was little more than a polyester T-shirt. Even our aerodynamic consultants expected limited gains, so we named the jersey Split Second, though, like now, we thought even small gains were worth pursuing. In the end the gains were pretty substantial, and we completely revolutionized the look of the pro peloton.We’re now on the sixth major revision of our aero jersey. Each generation has become more aero and better fitting.