90521-ZX2-C00 Gear (0.50) Shim D - Overview. The 90521-ZX2-C00 Gear (0.50) Shim D is an essential component within Honda marine engine systems. Designed specifically as a precise gear shim with a thickness of 0.50mm, it plays a critical role in maintaining accurate gear alignment and spacing. This shim supports the gear system by ensuring smooth mechanical operation and reducing wear caused by misalignment.. Key Features. Precision shim with 0.50mm thickness for optimal gear alignment.. OEM/genu