Behind the seats of an MX5 NB (1998 - 2000), a lot of interior air movement occurs during open driving. Roll bars and windshields intervene in just that area, adding extra structure behind the seats and reducing turbulence behind driver and passenger. This often provides more peace in the cockpit, especially at higher speeds. When the mounting points at the rear of the cabin are also solid and neatly mounted, such an addition fits nicely into the car's structure.
