If you have the money this is the sickest looking pipe and is as quiet as they claim to be. The pipe also smoothed out the power on my 2012 kx450f. It also gave it a deep throaty sound. I had absolutely no problem bolting the exhaust onto my bike.
The RS-4 muffler was developed in conjunction with the Rockstar Makita Suzuki Yoshimura race team with one purpose in mind: winning championships. That goal was accomplished during the 2010 AMA Supercross and Motocross season, as Ryan Dungey and his Yoshimura powered RM-Z450 shook the motocross world by being the first rookie in the history of the sport to dominate both series.
The new RS-4D builds on the technology that has made the RS-4 a force to be reckoned with on the racetrack, enhancing it's rock solid performance. By increasing the amount of open area at the exhaust outlet, the RS-4D increases airflow, resulting in smoother power delivery and increased throttle control. Testing has shown it offers increased horsepower and torque throughout the power curve, especially in the bottom to mid RPM range where riders need it most.