O.S. Max 75 AX ABL Aircraft engine with muffler has the same mounting dimensions as the O.S. Max .61FX. Advanced Bi-Metallic Liner process uses a double layer of plating material rather than one thick layer. This helps the metal bond to the cylinder and makes the plating more durable. Also, the plating process is more consistent, resulting in a more precise fit between piston and sleeve for better compression and longer life. Power Box muffler design provides more volume for increased power in a very compact shape. Angular head design offers increased surface area for better cooling Ball bearing-supported crankshaft. 61A carburetor with diagonally placed needle valve eliminating remote needle valve placement. Two year limited warranty.