The removal of traditional mechanical cables in favour of electrical wires eliminates poor shifting caused by contaminates corrosion and stretching and also provides effortless gear shifts and the shimano ultegra 6870 di2 sti give you all of this with di2 technology shifting is easy and precise a touch as soft as a mouse click is sufficient for the front or rear derailleur to instantaneously select the correct gear you can finely tune the reach adjusters of the levers to enable you to cus