These tires are made to fit vintage slot cars that are long out of production, but they happen also to fit certain  sizes of RS wheels as listed above.  We do not expect that they will be used on RS wheels as they come, but Ortmann tires are sandable and can readily be turned down to whatever diameter may be needed for a particular car.  See also the product page for each item in the RS wheels category for a list of Ortmann tires that fit it.