R-series rear derailleurs are designed to work with 8 and 9-speed Shimano-compatible road shifters. These R8 rear derailleurs have composite and steel parts that weigh more but have the same durability and performance as R9 and R10 derailleurs. - Steel pulley cage for extra durability - Not compatible with Shimano Tiagra 4700 road system - Short cage for double crankset and 28T max cog - Long cage for triple crankset and 28T max cog