Shimano HG80 Mega 9 cassette featuring light weight minimal design sprocket carrier- The 3 largest sprockets are mounted on a lightweight alloy carrier to reduce weight & increase rigidity- Hyperglide sprockets have a computer designed tooth configuration with contoured shift gates, resulting in a crisp smooth shift even under load- Close ratio gearing allows a more efficient use of energy through finer cadence control- Sprockets are cut away & drilled to reduce weight without reducing rigidity- For Super Narrow 9-speed HG chains