Seen these recently. They have little clear extensions (polycarbonate, I assume) on the aft edges of the mirror’s housing. I’m thinking the extensions help extend flow and taper it inward to reduce the wake, which is backed up by the site’s diagrams.
Anybody use something similar to these? A mirror delete makes more sense but the local police are ticket-hunters and the laws are vague so I’d prefer to keep two functional mirrors on the car.
Race Mirrors: World-Best Aerodynamics