Shimano Ultegra CS6500 9-Speed Cassettes.Must use 9-speed chainReduced cog spacing: 9-speed is same overall width as 8-speedAluminum carrier reduces weight and increases rigidityItem SpecificationsColorChromicaWeight176gIntended UseRoadCassette SpacingShimano/SRAM 9Cassette Body TypeShimano 9/10/SRAMCassette Cogs11,12,13,14,15,16,17,19,21Number of Speeds9Chain Compatibility9-SpeedRange11-21