Black Bicycle Freewheel Mountain Bike Cassette 8/9/10/11/12 Speed SHIMANO HG Structure Specification for SHIMANO/SRAM. Material: Steel (40T, 42T) / Steel + Aluminum Alloy (46T, 50T, 52T). For example: your old bicycle cassette is 10 layers, then you need to buy 10 speed bicycle flywheel.
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