in theory that was one of the big ideas behind cassettes. however shimano soon found out it was better to just seel tha whole cassette. if you can find just the 15t sure it is OK to replace just it.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk