R-series rear derailleurs are designed to work with 7, 8 ,9, and 10-speed -compatible road shifters. These R9 rear derailleurs combine the benefits of R10 and R8 rear derailleurs: compatibility friendly, weight saving, and robust. Weight saving aluminum bracket body and outer link. Steel pulley cage for extra chain-rub durability. Compatible with 7, 8, 9, and 10-speed road systems. Not compatible with Tiagra 4700 road system. Medium cage for double 34T setup. Item Specifications: Rear Derailleur Mount Type: 10x1 Standard, Drivetrain Speeds: 9,10, Cage Length: Medium, Chain Wrap Capacity (teeth): 39teeth, Largest Cog: 34, Color: Black, Weight: 291g, Rear Der/Shifter Compatibility: Road,