Borla's XR-1 catback exhaust for the Subaru WRX/STI features 3" piping with Borla's patented XR-1 multi-core muffer for optimal flow. This system does not use a resonator like the Hush, so it has a deep, powerful tone. The section of the catback that bolts to the downpipe is slip-fit, and can be replaced with the 3" adapter for future upgradability. For the WRX/STI, the downpipe section Borla includes will bolt perfectly to your stock downpipe, but the optional 3" adapter simply bolts on and removes the bottle neck if you plan to use a 3" downpipe. Backed by Borla's million mile warranty, and constructed of stainless steel -- this is a great performing catback for your WRX or STI.
The 3" adapter is designed for the XR-1 & Hush catback exhausts which have a slip-on downpipe connector. The 3" adapter simply slips into place and clamps down to replace the taper
Subaru STI 2004-2007
Subaru WRX 2002-2007