Improved surface treatment 9speed Lighter weight Wide link design SS model compatible with compact cranksets Total capacity SS 31T Cage Length Medium or Short Drivetrain Spacing ShimanoSRAM 8 Intended Use Road ShifterRear Derailleur Shimano Largest Cog 27 Chain Wrap Capacity 37 or 29 Derailleur Action TopNormal Traditional Color SilverBlack