Dual 2.25 diamter inlet, dual 2.5 outlet Resonator contains an internal H - Pipe for increased performance and improved sound. Use this resonator with 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 resonator. Built from premium T - 304 stainless steel, superior to T - 400 series knockoffs (such as 409), to give you the absolute best in performance and durability. Precision computer numerical control (CNC) manufacturing ensures an accurate fit. Best of all, BORLA stands behind every resonator with a Million - Mile Warranty. Just what youd expect from the worlds most experienced (and most winning) exhaust brand.