The new REDLINE HI-FLOW 3D PIPE(#9722) is special designed to fit with the Thunder Tiger RL-53H helicopter engine. Features enlarged exhaust volume, with smooth airflow to help the engine generate extreme power output and high torque at high RPM. Steady backpressure flow design to make the engine run smoothly under different RPM conditions. Fit with RL-53H engine, #9722 HI-FLOW 3D pipe will perform specifically at high RPM/high torque output while under the most demanding flight routines. It will be the best choice for the 3D extreme pilot.