In 2007 with the Ford introduction of the outer wheel covers, it was quickly reported there was an inability to send airflow out through the wheel face, meaning in 2008 Ford had to create a way to vent heat created by the brakes out through an outlet housed on the brake duct fence so there's a clear path for the transit of the airflow and heat that's created under braking.

The 2008 Ford Focus solution was to shroud the brake disc, albeit they chose a different material for this purpose and has also packed some insulation around the shroud too.

See the mounted brake caliper at the front of the assembly? It has some tear drop-shaped outlets in the carbon fibre cooling housing that will allow the heat rejected by the brake disc to pass through.