METICULOUS EVOLUTION. The Free Aero Race 4 Bibshort is our top race short, which also means that it's insanely comfortable even if you never pin on a number. The original Free Aero Race Bibshort was first introduced over a decade ago and has logged literally millions of kilometers under the backsides of our sponsored pro riders and has been the best-selling short both in the Castelli retail collection and in our Servizio Corse custom program. Over this time the short has undergone numerous updates and improvements in the never-ending quest to create the best short we can make. While the basic concept of a minimalist workhorse pro-level comfortable race short remains, every single fabric, component, stitch and construction method has been updated and improved over time. The fourth major generation of the short features the updated Progetto X2 Air Seamless seat pad. This pad separates a soft, stretchy skin care layer that moves with your body from a generously padded cushioning layer that replicates the form of your saddle. Eight-hour rides are no problem. Of course the fabrics are premium, made to our specifications by Italy's best fabric suppliers. The Forza fabric on the inner leg features 38% Lycra® content for perfect fit, while the Vortex fabric on the side panels is dimpled for aerodynamics. And it's held in place by the latest iteration of our seamless flat Giro leg gripper.