As an addition to the mechanical Dura-Ace 7900 series, the electronic Dura-Ace 7970 will deliver state-of-the-art technology that will give its users a revolutionary road riding experience. Di2 stands for ‘Digital Integrated Intelligence’. This innovative shift technology is still based on the Shimano Index System (SIS) that has proved its superior gear changing characteristics over the years. The big difference is that in this case , the shifting action is provided for by electronics instead of mechanics. This electronic shifting system was tested extensively over the past two years by several professional riders in all conditions possible, such as rain, mud, low temperatures, cobble stone roads and combinations of all of these at the same time. Dura-Ace 7970 series consists of Dual Control Levers, front and rear derailleur’s and a battery kit combined with remaining 7900 mechanical components. Shimano 7970 Dura-Ace Di2 Battery Charger Power Lead. UK plug lead to be used in conjunction with Dura-Ace Di2 charger.