Traxxas tuned pipe, resonator, r. O. A. R. Legal (dual-chamber, enhances mid to high-rpm power) (for revo with trx racing engines) 38-5493 description: the resonator dual-chamber aluminum tuned pipe is precision-engineered on the dyno to increase the mid to high-rpm power output of trx racing engines. Resonator pipes feature r. O. A. R. Legal stingers and come in single and dual-chamber versions. All resonator pipes are fully polished to a beautiful mirror-chrome finish with a laser etched logo. Mounting hardware is included. Replacement part for these models: revo accessory part for these models: slayer pro 4x4