The fastest jersey castelli have ever madeafter starting the aero jersey revolution in pro cycling castelli have continued to perfect this piece version 51 builds on the race leading aerodynamics while making the jersey more comfortable and durable updated fabrics on the front and back showed a 2 watt gain in the wind tunnel compared to the previous version but its not just aero its also extremely light coming in at just 103 g thats about 40 g lighter than a standard jersey and almost