87121-ZZ5-020 Rr (50) Mark - Overview. The 87121-ZZ5-020 Rr (50) Mark is a genuine OEM marking part used in Honda marine engine systems. This specific rear (50) mark supports the identification and proper assembly of Honda marine equipment, particularly designed to ensure reliable integration with Honda marine engine systems and their accessories. By maintaining factory specifications and tolerances, it ensures seamless fit and helps maintain the overall system's optimal performance and durabili