One after another, McLaren's shark fin

It just appears like every other week a team introduces its own shark fin engine cover, named by McLaren as a "top body dorsal fin". What's in a name. Needless to say, the item works similar as with Red Bull and its copycats, helping to maintain the car's stability while cornering. The rear cut-out around the rear wing's leading edge is at the same time preventing that the rear wing's efficiency would decrease when the car is in considerable yaw.
It's now a waiting game to see when Ferrari of BMW will come up with it, but don't be surprised if that's somewhere during this Hockenheim test too.