Shimano Ultegra SL Clamp-On Front Derailleur
The Ultegra SL Braze-On Front Derailleur (image of Clamp-On model unavailable from manufacturer).
Details
If you're looking for a quick-shifting super-light front derailleur, you've found it in Shimano's Ultegra SL. The wide pivot-link design suppresses flex for light, fast and precise shifts, even under load. And this fine derailleur is built tough for reliability and durability, too.
Your seat-tube diameter determines the needed derailleur clamp size.
Capacity is calculated by subtracting your smallest chainring's tooth count from the largest chainring's tooth count. Example: 53/39 chainrings: 53 - 39 = 14-tooth capacity.