This is the Magnum XL52 RFS Four-Stroke Aircraft Engine with Blue Rocker Cover. FEATURES: Aluminum piston, iron piston ring and steel cylinder sleeve for long life and high power output Dual ball bearing supported crankshaft and camshaft Dual needle valve carburetor insures precise fuel/airflow metering High-flow muffler One year limited warranty through manufacturer (valid only for engines purchased and used in the United States and its possesions INCLUDES: Magnum XL52 RFS Four-Stroke Engine with Muffler, instruction manual and parts list REQUIRES: Fuel: For break-in, 10% 2-stroke airplane blend For normal use, 15% 4-stroke airplane blend Glow Plug: 4-stroke type Break-in Propeller: 12x5, after break-in 11x7-8-9, 12x5-6-7, 13x4 Glow starter, fuel tubing and field equipment SPECS: Displacement: 0.52 cu in (8.53cc) Bore: 0.90" (23mm) Stroke: 0.83" (21mm) Practical RPM: 2,000 - 10,500 Weight with Muffler: 15.7 oz (445g) Distance Between Mounting Holes Same Side: 0.69" (17.5mm) Distance Between Mounting Holes Opposite Side: 1.7" (44mm) Width at Mounting Tabs: 2" (50.9mm) Height from Bottom of Mounting Tabs to Rocker Cover: 3.2" (82mm) Height from Bottom of Crankcase to Rocker Cover: 3.8" (96mm) Distance from Backplate to Front Bearing: 2.7" (68.7mm) Distance from Backplate to end of Crankshaft: 4.3" (109mm) High Speed Needle: Turn in completely then back out 2-1/2 turns Low Speed Needle: Do NOT adjust until engine is broken in. Hold carb barrel open, turn needle screw counter-clockwise until it stops then turn in clockwise 4 turns-this is the factory setting COMMENTS: Some Differences Between 4-Stroke and 2-Stroke Engines; 4-strokes are quieter. 4-strokes get better fuel economy. 2-strokes generate more RPM. 4-strokes generate more torque and will swing a larger prop. 4-strokes have a realistic sound, like a real aircraft engine. jxs 8/31/09 ir/jxs