Naraku 50cc QMB139 4-stroke Black Crossover Exhaust with Carbon Fiber Silencer.The crossover exhaust is tailored to the QMB139 engine and provides a top end performance boost. Available in a black finish with a real black carbon silencer for maximum stealthiness! Head Pipe Bolt Hole Spacing: 50mm Head Pipe Inner Diameter: 20mm Includes Removable Silencer Does Not Include Mounting Bolts