A single programmable shifter button in each unit, designed to fit cleanly into aerobar extensions. Works perfectly with Shimano's Di2 Synchro Shifting: each "up" shift moves to the next gear ratio considering both front and rear derailleurs, each "down" shift does the reverse.
Shimano's Di2 technology provides easy, precise, fast, configurable, shifting. A light touch instantaneously selects the chosen gear. Traditional mechanical cables experience "stretching", stickiness and corrosion which affect shifting, Di2 makes gear selection effortless and consistent.