90302-ZW5-U21 Hex (5mm) Nut - Overview. The 90302-ZW5-U21 Hex (5mm) Nut is a specialized fastening component essential for securing various assemblies within Honda marine engine systems. This nut supports the rigging and accessories system, playing a crucial role in maintaining mechanical integrity and ensuring reliable operation of marine equipment. Designed to Honda factory standards, it ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Feat