The Shimano Sora HG50 9 Speed Cassette features Hyperglide sprockets which have a computer designed tooth configuration with contoured shift gates, resulting in a crisp smooth shift even under load.Key Features:High quality 9-speed cassetteHyperglide sprockets have a computer designed tooth configuration with contoured shift gates, resulting in a crisp smooth shift even under loadClose ratio gearing allows a more efficient use of energy through finer cadence controlSprockets are cut away and drilled to reduce weight without reducing rigidityNickel-plated finish offers hard wearing resistance to corrosionCorrosion-resistant steel cassette lockringFor Super Narrow 9-speed HG chainsAverage weight 270 g for 12 - 23T