Resonator features an internal H-Pipe for increased performance and improved sound. Use this resonator with BORLA® Cat-Back™ systems 140590 and 140591 to create a quieter sound. It is NOT intended for use with other systems. This is NOT a stand alone muffler/ resonator. 2.25" into 2.5" diameter part. Built from premium T-304 stainless steel, superior to T-400 series (such as 409) to give you the absolute best in performance and durability. Precision computer numerical control (CNC) manufacturing ensures an accurate fit.