These highly polished 1 1/16" dia. chrome steel balls are machine lapped to a grade 25 finish specification (1.0 micro inch "RA" or "mirror" finish). To the naked eye they are more finely polished than standard BRF (bright finish) OEM carbon steel pinballs. Chrome steel balls retain magnetism and shouldn't be used in machines with magnets. (see "choosing the right ball" button above) They are harder and more rust resistant than carbon steel balls and will last longer before requiring replacement.