I have an 2006 OEM WRX axle back that was professionally gutted by "Muffler Man". It's now running a 2.5 inch straight pipe all the way through from the axle back pipe to the actual tip of the muffler. It sound's a very similar to the SPT / Cobb exhaust. The axle back piping is also 2.5 inches. There are NO leaks and NO rust. If your looking for a stealthy looking exhaust, this is it . Asking 50$ picked up in Anaheim Hills OR 80$ shipped.