Are you sure it is a complete 21.2 package and not just a 21.2 stem on a real thick steerer?
I would search for some threads mentioning 21.2 HS and stems.
Might be a trial and error thing.
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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"
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