Triathletes and time trialists will love both the aerodynamics and convenience of the Shimano SW-R671 Di2 Bar End Shifters. Each shifter has two buttons and plugs directly into the aero bars, and sticks straight out, effectively extending the extension. With them, you don't have to decide how to position your shifters for maximum comfort or optimal aerodynamics. It's aero and comfortable at the same time. There is 300mm of wire attached to each shifter, so it will fit on even the longest aero bars.
While it's a natural to pair these with ST-9071 dual-control levers, you can also pair them with Shimano's drop bar Di2 dual-control levers, ST-9070, ST-6770 or ST-R785. This makes shifting a piece of cake for those who like to slap aero bars on their road bike for hilly events. In both cases, you'll need the five-port junction box to handle the wire traffic.
The shifters can be programmed and reprogrammed via Shimano's SM-PCE1 system programming hardware.