This is the Piston Ring for the O.S. GT55 Airplane Engine (OSMG1555) This is located on the piston and provides proper clearance in the cylinder wall. FEATURES: Steel construction Replaces warn or damaged piston rings INCLUDES: One Piston Ring - part #3 on engine part list REQUIRES: Assembly onto piston SPECS: Diameter: Approx. 42.5mm (1.67") COMMENTS: For the Piston Pin order OSMG7770 For the Pin Retainer order OSMG7500 For the Connecting Rod order OSMG4035 For the Cylinder Liner order OSMG5400 OS EnginesPart OSM29703400