Shimano Ultegra Di2 ST-R8050 STI Levers
With Di2 technology shifting is easy and precise - just a light touch, as soft as a mouse click, is sufficient for the front or rear derailleur to instantaneously select the correct gear. 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.
Simply pressing tactile buttons allows effortless and comfortable shifting even when your hands are cold. Drop bar STI with shift buttons located in a near identical place to the positions you'd assume shifting using a mechanical Shimano STI.