Shimano Tiagra HG-50 9 speed 12-25 cassette - 2018
HG50 9-Speed Computer designed Hyperglide (HG) sprockets incorporate specifically positioned shift ramps and tooth profiles for improved chain control during shifting. Fast and responsive indexed shifting is the result.
Must use 9-speed chain
Reduced cog spacing: 9-speed is same overall width as 8-speed