The rear beam wing previously did this job, but the 2014 regulations have banned that so teams are looking for new ways to make up for it.
The interesting thing about this package is that when the car is at higher ride height, these sections will almost completely close the gap at the top of the diffuser, helping it to work at low speed.
At higher speed, because of suspension deflection, a gap will open up between the bottom of the lower blocker and the diffuser, which will reduce drag.
So this makes it a double whammy, giving you more downforce under braking and in slower corners and less drag at high speed.
This could be McLaren's secret weapon because, if it does work, it is not something that can be copied in five minutes as it is dependent on a number of design parameters at the rear of the car.
