Shimano's Ultegra Di2 Front Derailleur makes the dream of lightning-quick front shifting a reality. Its intelligent electric brain senses the location of your chain, providing impossibly fast, smooth and accurate shifting, even under load, with just the push of a button on your Ultegra Di2 shifter (sold separately). It also auto-trims to maintain clearance between the chain and cage no matter what chainring/cog combination you choose. You'll never miss a shift again and will hit the right ring faster than ever. And, because there are no cables and housing to stretch, wear or fail, you'll also love Di2's amazingly durable, reliable and silent operation.
Capacity is calculated by subtracting your smallest chainring's tooth count from the largest chainring's tooth count. Example: 46/34/24 chainrings: 46 - 24 = 22-tooth capacity.