Shimano Tiagra HG50 9-Speed Cassette. Must use 9-speed chainReduced cog spacing: 9-speed is same overall width as 8-speedItem SpecificationsColorSilverWeight436gIntended UseMountainDrivetrain SpacingShimano/SRAM 9Cassette Body TypeShimano 9/10/SRAMCassette Cogs11,13,15,17,20,23,26,30,34Speeds9Chain Compatibility9-Speed