Top Rear Tail Fairing (single kit)Developed by pilots using the same principals of airplane wings, our aerodynamic rear tail fairings attach to the top at the rear of your semi truck trailer. This directs air to move smoothly around the back of the trailer; significantly reducing the vacuum pocket and allowing your trailer pull with less power. 4% increased MPG when installed on the rear top and both sides of trailer (see side fairings below) Aerodynamic design reduces vacuum pocket,