Treadstone Performance Engineering is once again is proud to announce the release of their famous flex couplers in two new sizes 3.50" and 4.00". Flex couplers are used to isolate engine vibration to your exhaust components, and prevent cracks in your downpipes, cat-backs headers and turbo manifolds. We have introduced Stainless Steel Flex Couplers that have bellows with interlocking lining to help increased exhaust flow through the coupler, and prevent excessive back pressure to build. Standard flex couplers either have a braided inner liner that in time will burn out creating an obstruction in the exhaust track, or others with a flex bellow that creates turbulence when exhaust gases flow through. These are the only type of flex coupler that can withstand high pre-turbo exhaust temperatures, meaning you can use these flex couplers when complex turbo header designs are needed to prevent turbo header cracks. Perfect for turbo downpipes! We use these in our WRX turbo kit up pipe! Click Here For More Info!