A Cab Roof Deflector is a straight piece of plastic or fiberglass that extends from the top of the cab at an angle. It usually has open sides and may be retractable.
A Cab Roof Fairing is a roof fairing that extends partially over the cab of the truck with enclosed sides. It may not line up perfectly with the sides of the cab.
A Cab Side Fairing is Extends downward from the Base of the cab between the wheels of the Tractor, covering the open space and streamlining the Fueltank(s). Most Cab Side Fairing