Jett Engineering Sport Muffler fits the Rossi 45, 53 OS Max 46, 50, 55 FX, AX, SF (and all Clone Engines).
THE SPECS ARE:
Muffler/Pipe Body Diameter: 1.5 inch (38 mm)
Muffler/Pipe Length: 7.5 inch (190 mm)
Mounting Screws Center to Center Distance: 1.45 inch (37 mm)
Muffler Weight: 3.6 oz (102 grams)
Tuned RPM Range: 13,000 to 17,000 RPM (Depending on the make of the engine)