Shimano's SLX Front Derailleur is built tough for enduro/all-mountain use and it shifts quickly and smoothly every time. Shimano tweaked the angles for improved rear tire clearance and easier access to adjustment screws.
Your seat-tube diameter determines the needed derailleur clamp size. This front derailleur comes with a 34.9mm clamp and adapters for 28.6 and 31.8mm seat tubes.
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.