Shimano Ultegra CS6600 10-Speed Cassettes.Ultegra CS-6600 cassettes with a 13-16-tooth first-position cog are not compatible with Dura-Ace FH-7800 hub or WH-7800 wheelCompatible with all 10- and 9-speed Shimano hubs except for 13-16-tooth first position cog cassettes which are not compatible with DA FH-7800 hubs or WH-7800 wheelsItem SpecificationsColorChromeWeight245gIntended UseRoadCassette SpacingShimano RD 10,SRAM 10Cassette Body TypeShimano 9/10/SRAM,Shimano 10-D (deep spline)Cassette Cogs15,16,17,18,19,20,21,22,23,25Number of Speeds10Chain CompatibilityShimano 10,SRAM 10Range15-25