---Manufactured from high quality T304 grade stainless steel ---Free flowing catalyst replacement to get the most from the EJ20 and EJ25 boxer engines ---Designed to fit the original and most aftermarket exhaust systems ---3" bore tapering down to 2.5" at the outlet ---Sold for off road and track use only Compatible with: --- Subaru Newage WRX STi 2001-2007 models.