The Carbon Fiber Titanium Hi-Power Catback for the 2002-2007 WRX and STI has all the features of the regular exhaust: 75mm piping, a resonator, non-tapered piping, and an angled-exit muffler, but, as the name implies, the Carbon Titanium features a carbon-fiber wrapped stainless steel muffler with a titanium tip and full SUS304 stainless steel piping. The HKS Hi-Power Carbon Titanium's full straight, 3" piping and free-flowing muffler reduce backpressure and create significant performance gains while giving your WRX or STI a deep, throaty exhaust tone.