This is the Shimano DI2 Dura-Ace E-Tube Junction Box. This box is referred to as the junction Box A and is located at the handlebars on a Di2 build. The box is available in either a three or five port option, to accommodate either a one pair or two pair shifter arrangement. Features: SM-EW90-A: 3-Port Cockpit Junction Box connects 1 pair of Di2 shifters to the frame junction box via 3 SD50 E-tube wires SM-EW90-B: 5-Port Cockpit Junction Box connects up to 2 pairs of Di2 shifters to the frame junction box via 5 SD50 E-tube wires OEM front wiring kit for Dura-Ace Di2 9070 LED battery charge level indicator Rear Derailleur adjustment mode Internal Battery charging port Use Di2 system checker to update component firmware from http://e-tubeproject.shimano.com/ All Di2 components on the bicycle require the same firmware version. Using Di2 components with different firmware versions may cause malfunctions