The Zero/Sports World League Catback Exhaust has been designed to meet the highest standards in the Japanese market. In addition to being made of the highest quality materials, it has also attained the difficult JASMA recognition. The unique design of this exhaust allows exhaust noises to be kept to a minimum while allowing maximum performance. This exhaust also keeps that trademark Subaru boxer rumble perfectly intact. The loudness of the exhaust never exceeds 92dB, and stays at a quiet 70dB while cruising. Acceleration only increases the loudness level to 78dB. The overall diameter of the exhaust piping is 3”.