Tested in Kona and proven at the Tour de France, the new VukaR2C aero shifter is a milestone in our efforts to develop cockpit components that combine high performance aerodynamics with superior ergonomics.Once you position the lever at the natural angle for your hand position, the VukaR2Cs return to center actuation resets the lever to its original angle after every shift, keeping you as low and as comfortable as possible.Weighing just 180 grams per pair, the VukaR2C is also the first plug in shifter designed with an aerodynamic profile that saves up to 6 seconds over 40km compared to a standard lever. The VukaR2C is a plug in shifter compatible with ShimanoSRAM 10 speed only. The VukaR2C fits most aero bar extensions, but is optimized for use with a new version of Zipps VukaShift extensions. There are 2 bolts on the Vuka R2C Shifters. One uses a 4mm allen wrench and one uses 5mm allen wrench. The 4mm bolt see picture is used to attached the shifter to the shifter boss for installation into an aero bar. The 5mm bolt is used to keep the shifter assembly in one piece. The 5mm bolt can be loosened to adjust the angle of attack of the shifter lever, but should NEVER be removed. Removing the 5mm bolt can cause the shifter to come apart, this will ruin your day. If you have disassembled the shifter please call Zipps technical experts at 1 800 346 2928. They can help you get the shifter back together.