A flex pipe is a pipe that is generally fabricated from stainless steel or forged steel.  This flexible pipe functions like a connector and provides flexibility within the exhaust system.

The flex pipe is a valuable component that is used for both front wheel and all wheel drive motor vehicles. During vehicle acceleration and rough road conditions, the motor in your car will vibrate and the flex pipe safeguards your exhaust system from damage. The flexibility produced by the flex pipe helps prevent your exhaust system from breaking due to the swaying  motion.