The Aero Race MR made its debut on the feet of David Millar and Team Garmin at the 2013 Tour de France. The brilliant two piece design has the aero front panel for wind piercing and a vented mesh rear panel for breathability. The mesh panel is elastic, so putting the covers on is a snap. Let's recap. Castelli made the shoe cover aerodynamically correct, easy to put on/remove and vented. Anyone who has some experience with shoe covers would tell you it's hard, if not impossible to fine one product that does all of these action points.
The Aero Race MR cover was developed using CFD (computational fluid dynamics) modeling. then tested in the wind tunnel. The combination has yielded the finest aero shoe cover in existence. Other highlights included a slight silicone leg gripper for no slip fit and a YKK Camlock zipper. The recommended temp range for these covers are 59° and up, so they can be used for more than strictly aero purposes if you want to take the edge of on slightly cooler days.