Never worry about cable tension or derailleur adjustment again. Simply measure four main wire lengths to accommodate your frame size, plug them into their watertight connections and you're ready to ride. The Shimano Ultegra DI2 6770 Electric Wire comes in 13 difference lengths so you can customize the wiring setup for your frame. Each EW-SD50 wire is waterproof and can be routed externally or internally. Best use for each wire length will usually be: 300-400mm for junction box to front derailleur, 500-600mm for junction box to rear derailleur, and 650-950 for junction box to shift levers or unique routing.
Simply take four measurements on your frame: 1) Center of bottom bracket to rear derailleur (allowing for extra loop to derailleur). 2) Center of bottom bracket to front derailleur. 3) Center of bottom bracket to downtube water bottle cage (for battery). 4) Center of bottom bracket to front of stem.