The shimano st 6870 features di2 technology shifting for easy and precise control just a light touch as soft as a mouse click is sufficient for the front or rear derailleur to instantaneously select the correct gear programmed automatic motion at the touch of a switch makes this derailleur quick smooth and effortless to shift the removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates corrosion and stretching but p