THIS IS THE O.S. MAX .55AX ABL AIRPLANE ENGINE WITH MUFFLER. FEATURES: BALL-BEARING SUPPORTED CRANKSHAFT, DIAGONALLY PLACED NEEEDLE ON 40J CARB, SAME MOUNTING DIMENSIONS AS 46 AX, ABL CYLINDER LINER CONSTRUCTION, #8 GLOW PLUG, POWER BOX MUFFLER, INSTRUCTION MANUAL, ABL CONSTRUCTION REQUIRES: 5-20% NITRO FUEL, BREAK-IN PROP, FUEL FILTER