Shimano Ultegra 9 speed 12-25 cassette – 2018 Ultegra CS6500Must use 9-speed chainReduced cog spacing: 9-speed is same overall width as 8-speed Aluminum carrier reduces weight and increases rigidity. Posted in Bicycle Cassettes & Freewheels, Bicycle Drivetrain Parts, Bicycle Parts, Cycling, Outdoor Recreation, Sporting Goods