This is the Silencer (Muffler) for the O.S. 46 AX (OSMG0547) and the 55 AX (OSMG0556) aircraft engines. FEATURES: Power Box design for quiet operation Fully positionable O-ring between front and rear body to prevent oil leakage INCLUDES: Silencer (Muffler) for the O.S. 46 AX and 55 AX aircraft engines REQUIRES: Fastening to crankcase with Muffler Screws, OSMG6914 SPECS: Length: 5.1" (129mm) Diameter: 1.5" (38mm) COMMENTS: For Assembly Screw, order OSMG6943 For O-Ring, order OSMG7365 jxs 9/03/08 ir/jxs