Shimano's SLX Front Derailleur is made for long-travel, all-mountain bikes with a double ring set up. The compact cage design gives you improved rear tire clearance while the matched radius reduces chain drop. The dual-pull design allows this derailleur to be used with top- or bottom-pull cable routing too. It's super stiff for the quick, authoritative shifts that serious mountain bikes demand.
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.