The Roush Performance ACTIVE Axle Back Exhaust is a lot more than just an exhaust system. Sure, this system features the famous Roush Stainless Steel Exhaust system that you've seen in the past, but this system goes a step further. What is an ACTIVE exhaust system? The Roush Active Performance Exhaust System allows you to take an active role in controlling your exhaust system flow, sound, and performance. With simply on the fly tuning via an in car dial, you can choose between four different exhaust styles in seconds. Touring Mode: This is the quietest setting and keeps the exhaust valve closed for times when you want things as quiet as possible. Sport Mode: This setting changes based upon your RPMs and how far you have your foot on the gas. Sport Mode keeps the exhaust quiet during normal driving conditions, but the harder you start pushing the vehicle, the more the valve opens up and the exhaust system wakes up. This is the most popular setting for every day driving. Track Mode: This is the most aggressive setting. The exhaust valve is fully open at all times. This is the highest performance, as well as the loudest setting. Sound levels may exceed local sound ordinances when at high RPMs, so we only recommend using this setting at the track racing. Custom Mode:. You can create a custom sound map by tapping into the heart of the exhaust system management unit via the exhaust's integrated wifi connectivity and iphone application. You'll have full control of the valve positions based on speed, RPMs, and accelerator position. Roush Exhausts are made from stainless steel and are finished with a chrome flashing process. The exhaust tips are embossed with the Roush logo. Roush Exhausts are completely bolt on and can be installed with minimal effort. All necessary hardware and instructions are included. The part number for this item is Roush 421928 and it fits 2015-2017 Ford Mustang (2.3 EcoBoost Trim levels 200A/201A) with a Roush Rear Valance. If you have not upgraded to a Roush Rear Valance, this exhaust will not fit.