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