This is the 1.2x54mm O-Ring for the O.S. Engines GT55 Gasoline Airplane Engine (OSMG1555). FEAUTRES: Rubber construction Black in color Used as cover plate gasket INCLUDES: One 1.2x54mm O-ring - part #21 in engine part list REQUIRES: Installation on crankcase plug lmm 04.13.10 ir/jxs