Perhaps the size of the comb in which the worker bees are raised isn't
quite the right issue. The issue would seem to be the maximum spacing which
will still prevent any queen from passing through, rather than the right
spacing for allowing workers to pass through.

Whatever the size of the worker brood comb, queens are raised in different
sized cells. While queens from different breeds probably vary in average
size, the smallest may still be prevented from going through an excluder
which will allow the largest workers passage. In which case we only need
one size excluder on the market.

Tom Swanky
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