This is the Replacement Muffler for the OS MAX 25SF and 25FX Engine. FEATURES: Mufflers Have Aluminum Construction. Expansion-Type Design for Maximum Muffling. INCLUDES: One Muffler Two 3mm x 28mm Muffler Mounting Screws One pressure fitting FEATURES: Muffler Comes Pre-Tapped. SPECS: Overall length: 108mm (4.26") Diameter: 30mm (1.18") Center to center of mounting holes: 35mm (1.379") Rectangular exhaust port: 29mm x 6.5mm COMMENTS: Pressure fitting is pre-installed. NNA 2/24/02