40204-ZW1-000 Extension Case Grom - Overview. The 40204-ZW1-000 Extension Case Grom is a critical rubber sealing component within Honda marine engine systems. It supports the extension case system by providing a watertight seal that protects sensitive engine parts from water, debris, and vibration. Engineered to meet precise factory specifications, the grommet ensures seamless integration with existing parts, maintaining optimal performance and durability.. Key Features. Durable rubber grommet designed specifically for the extension case on Honda marine engines.. Provides an effective seal to prevent water intrusion and contaminants from reaching internal engine components.. Manufactured to OEM Honda standards ensuring exact fit and long-lasting reliability.. Helps minimize vibration and enhances mechanical longevity of the extension case system.. Seamlessly integrates with Honda marine engine systems, maintaining factory performance and protecting critical components.. Compatible with