Williams has been forced to sacrifice the aerodynamic philosophy it usually deploys on its front brake ducts in Mexico, as the Grove-based team looks to play the long game.
Ordinarily it uses a plain vertical fence devoid of any airflow inlets, making it reliant on air passing between the fence and the tyres sidewall.
This lessens the brake ducts' aerodynamic impact, however, such are the cooling demands in Mexico, as due to the circuit's altitude it has had to compromise adding a small vertical slot near the leading edge of the fence to collect airflow.
It could risk using its standard configuration brake duct and win a little more aero performance for qualifying but during the race that risk could expose it to a brake failure.
That's something that it can ill afford with just three races to go, especially on a track that lends itself to the FW38's straightline speed and should see both drivers net a decent haul of points.