The SUPER TURBO MUFFLER has the same pipe diameter as the Dual Muffler, that had been released previously. Using the latest HKS technology we had succeeded in controlling the sound and keeping the volume low. We recommend this product for those, who are equipped with a catless downpipe and who are wanting to suppress the exhaust sound as much as possible. Full straight exhaust layout eliminates narrow points and improves exhaust gas flow, allows to enjoy a moderately sporty sound while eliminating unpleasant drone sound. Complies with Japanese noise regulations. Inspection-Ready Muffler: designed to maintain a sporty sound while suppressing unpleasant ones. This is a muffler for vehicles that need to pass strict Japanese domestic noice standard inspection. This is Factory Exhaust Valve Compatible which can be switched between Sports and Normal Mode when desired.