90503-ZZ5-M01 Plain (6mm) Washer - Overview. The 90503-ZZ5-M01 Plain (6mm) Washer is a fundamental component designed for Honda marine engine systems. Its primary role is to evenly distribute load and prevent damage to surfaces when fasteners are tightened, ensuring reliable and consistent operation of the equipment. Engineered to seamlessly integrate into various mechanical assemblies, this plain washer plays a crucial part in maintaining the structural integrity and operational reliability of