CASSETTE SHIMANO HG-50 TIAGRA 12-23 9S.

Precision 9-Speed Cassette Sprockets ( 9-speed performance from precision HG sprockets and ultra-narrow chain. No increase in sprocket cluster width allows retrofit to 8-speed freehubs). HG Sprocket Design (Computer-designed HG (HyperGlide) sprockets insure fast and quiet down-shifts as well as instant up-shifts without hesitation). Interchangeability (The 9-speed sprockets are made to the same specifications as those used in the 9- speed Dura-Ace, Ultegra, and 105 groups, so there's complete interchangeability).