Shimano's Tiagra Clamp-On Front Derailleur provides quick shifting. And, the clear-coated aluminum body and plated-steel cage are extra durable so you can enjoy smooth shifts mile after mile.
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.