ScootsUSA 190-47-6127 QMB139 50cc, 4-stroke Performance Exhaust - Oval Stainless Steel Oval After-Market Performance Exhaust for QMB139 50cc 4-stroke engines. Oval Muffler Head Pipe Bolt Hole Spacing: 50mm Head Pipe Inner Diameter: 20mm Muffler Overall Length: 15 inches Includes Removable Silencer Includes Mounting Kit