For quick, dependable shifting, look no further than Shimano's Sora Front Derailleur. Sora front derailleurs are compatible with dual-control road shifters and flat-bar style Rapidfire Plus shifters.
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: 46/34/24 chainrings: 46 - 24 = 22-tooth capacity.