XTR, XT, Dura Ace, Ultegra, and Alfine all have a technological innovation of the computerized shifting system based on the Di2 concept known as Shimano Electronic Intelligent System. The SEIS 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 has been extensively tested over the past two years by several professional riders in all conditions possible, such as rain, mud, low temperatures, coble stone roads and combinations of all of these at the same time. Shifting is executed by simply pressing the button. No power is needed to shift, which gives important advantages since it is easier to always keep a tight grip on the handlebars and to keep your concentration on riding instead of shifting. The shift system allows accurate and effortless shifting in difficult circumstances for example when you have cold hands or when you are completely exhausted. Furthermore, the shifting performance will never be affected by contaminates or stretching cable since the shifting signal is transferred electronically. The operating buttons work similarly to mechanical Dual Control levers so you don’t need to re-program your mind for SEIS.