This is a pair of replacement O.S. Engines 3x7mm Push Rod O-rings, intended for use with the O.S. 91HZ F3C, and 91HZ-PS 3D Helicopter Engines, as well as the O.S. FS-110-a, FS-120S-E, FS-120 III, FS-200S-P and FS-200S four stroke airplane engines.
NOTE: This part may be compatible with other O.S. engines. Please check your owner's manual and cross reference the part number to verify that this is the correct part for your engine.