This is the optional Traxxas Resonator Dyno-Tuned Performance Pipe for the Revo 2.5 and 3.3. FEATURES: The Traxxas Resonator aluminum tuned pipe for Revo is specifically engineered to fit right in the chassis and complement Revo's racing engine. The single-chamber design dramatically increases bottom-end punch by nearly 20% between between 10,000 and 15,000rpm, and continues to pull strong with a 10% increase from 15,000 to 30,000rpm. It's perfect to provide that extra snap of acceleration off the line. INCLUDES: One optional Traxxas Resonator Tuned pipe for the Revo REQUIRES: Traxxas Revo with TRX Racing Engines COMMENTS: Tuned pipe, Resonator, R.O.A.R. legal (single-chamber, enhances low to mid-rpm power) JBM 1-12-06 ir/jxs BOX DIMENSIONS: 3.25" W. X 1.88" H. X 8.88" L. BOX WEIGHT: .20 LBS.