QD EXHAUST Aprilia RSV4 (2021+) X-DB the Sound Controller (Euro5 homologated)X DB sound controller by QD Exhaust for the Aprilia RSV4. The X DB sound controller by QD Exhaust is a revolutionary modulation kit designed specifically for the Aprilia RSV4. This innovative QD Exhaust product seamlessly integrates with the stock wiring and utilizes all OEM components of the bike, including the valve, servomotor, and cables. With the X DB controller, riders have complete control over their exhaust valve, allowing for precise