I received a WH-RS21 wheel set from a customer.
Both front and rear wheels were perfectly centered with virtually no runout.
Interestingly, the front hub's ball bearings were adjusted too tight,
so I loosened them to proper tension.
（Bearing play is actually quite common, so）
I received another WH-RS21 wheel set from a customer.
Both wheels were perfectly centered. The front wheel had minimal runout,
and the rear wheel had some lateral runout that the customer had reported,
but it was only in one spot and presents no real issues.
Of course, these are separate jobs (just to be clear).
Both customers bought from the same shop,
but four straight Shimano wheel sets coming in perfectly centered
is virtually unheard of—so they must be doing proper inspections before sale.
Both front and rear wheels were perfectly centered with virtually no runout.
Interestingly, the front hub's ball bearings were adjusted too tight,
so I loosened them to proper tension.
（Bearing play is actually quite common, so）
I received another WH-RS21 wheel set from a customer.
Both wheels were perfectly centered. The front wheel had minimal runout,
and the rear wheel had some lateral runout that the customer had reported,
but it was only in one spot and presents no real issues.
Of course, these are separate jobs (just to be clear).
Both customers bought from the same shop,
but four straight Shimano wheel sets coming in perfectly centered
is virtually unheard of—so they must be doing proper inspections before sale.