Circuit Werks latest 2003-2006 350z & Infinty G35 2003-2005 Test Pipes with Anti Reversion Chambers. These are the newly designed unlike just a typical straight pipes, this will help with the sound of your VQ motor, smooth out the exhaust flow, and not to mention the additional performance gain versus any typical test pipes. Fits both Auto and Manual transmission. These test pipes feature a 2.5" outer diameter with a 2.25" inner diameter design, Built in flex pipes to absorb all the movements from your motor and is a Direct bolt on with built in o2 sensor extenders. Sorry, no instructions and please note that this replaces your factory catalytic converter and might not pass emissions in some States. Off road use only. Other models are also available.