SRAM's X0 Front Derailleur is made from cold-forged aluminum and chrome-plated steel for exceptional reliability and a race-worthy weight. It boast’s SRAM’s X-Glide technology for super-smooth and lightning-quick shifting even under load. This 38/36T maximum chainring size version is the one you want if you are running a low-range double-ring setup.
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.