The S-Works Tarmac SL7 Dura-Ace Di2 is one of the latest top-end offerings from Specialized that now focuses just as much on aerodynamics as it does on weight – or lack of it. The frameset has seen various tweaks over its predecessor, and when paired with aero components like the handlebar and wheels makes the SL7 a very, very fast bike indeed. This model comes at an eye-watering price, though.