Close look at high-resolution maps for large continental strike-slip earthquakes shows that surface ruptures are formed of fault segments. These segments are bounded by fault bends and step-overs, or combination of the two. The lowest limit in size for such segments might not be relevant to understand earthquake mechanics as it pertains to the granular properties of the breaking medium. The maximum limit in segment length, however, is important as it is directly related to the maximum extant of seismic rupture. Using a set of 10 strike-slip earthquake rupture with similar high quality maps, we show that segments seem to have a maximum length of ~18km, independent of regional tectonic setting. Although slip-inversions for earthquakes, based on seismological and/or geodetic data, most often are not unique and could show quite some variability even for the same event, depending on the authors, some gross characteristics seem to persist that are relevant to earthquake mechanics. Measurements of maximum horizontal extent of individual slip-patches derived from seismic source inversion for strike-slip events show that their dimension does not increase infinitely with magnitude but instead reaches a maximum value of ~25km. These two independent lines of observations, complemented by earlier data and analogue experiments, suggest that some external parameter controls the structural scaling of the length of seismic segments, independently of individual earthquakes. We propose this controlling parameter to be the thickness of the seismogenic crust.