91353-921-310 O-Ring (5.5mm) - Overview. The 91353-921-310 O-Ring (5.5MM) is a critical sealing component used in Honda marine engine systems, primarily within the fuel system of various Honda marine outboard engines. Its main function is to create a watertight seal between mating parts, preventing fuel and water leaks and maintaining system integrity. Designed to exact OEM specifications, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key F