Vehicles involved in rollover accidents almost always leave a debris trail. This debris trail is useful for the accident reconstructionist; it assists with identifying the vehicle path during the rollover and the location and orientation of the vehicle at various vehicle to ground contacts. Often it is helpful to know when and where various vehicle windows fractured. This is possible by comparing glass obtained from the accident site with glass samples still attached to the accident vehicle. The limit of this analysis is controlled by the manufacturing tolerance of the vehicle glass and the specified pane thickness. This paper presents a series of measurements made on various automotive tempered windows and presents: 1) the thickness range in individual panes, and 2) the thickness variation seen from pane to pane in the same vehicle.