When setting up your Di2 electronic shifting for road or TT/Tri bikes, you have the option of connecting up to four shifters. For road these may be the standard Dual Control with sprinter or climber locations for satellite shift buttons. For TT/Tri you can use aerobar end buttons as well as those located on the brake levers. A total of four shifting wire ports covers those choices, and the fifth port is to attach the downtube port connecting wire. The under-stem mounted Di2 E-Tube SM-EW90A-B 5-Port Junction Box also features an integrated battery level indicator, charging port, and gear index setup switch.