90303-ZX2-C00 Nut Hex (18MM) - Overview. The 90303-ZX2-C00 Nut Hex (18MM) is an essential fastening component designed to support Honda marine engine systems. This 18mm hex nut plays a crucial role in securing various engine parts, ensuring the overall reliability and performance of your marine equipment. Crafted with precise engineering to match factory standards, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. High-quality 18m