Shimano's SLX FD-M671 Front Derailleur is made for long-travel, all-mountain bikes with a triple-ring set up. It's a down-swing, top-pull derailleur, great for full suspension bikes, 29ers and especially full-sus 29ers. The compact cage design gives you improved rear tire clearance while the matched radius reduces chain drop. It's super stiff for the quick, authoritative shifts that serious mountain bikes demand.
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.
Bottom-pull derailleurs are used when the cable is routed underneath the bottom bracket and up through the cable clamp. Top-pull derailleurs work with frames where the cables are routed down from the top tube.