While Shimano was the first drivetrain brand to offer up an electronic system (2009), they are the last of the “Big Three” to make the move to 12-speeds for drop bars. However, unlike the others, they are maintaining the same hub body, which means that for consumers that want to upgrade, 11-speed wheels are compatible with the new cassettes without any modifications.
Shimano is launching with two cassette offerings,11-30 and 11-34, and will have an 11-28 next year. Shimano is also maintaining their existing chainring offerings with 50-34 and 52-36, but adding a new 54-40. There will also be a few larger sizes for triathlon and pro racers, but Shimano is planning on the 50-34 and 52-36 being the most popular. In addition, they are offering a 160mm crank through 175mm lengths, with Dura-Ace adding 167.5mm.