90405-ZZ5-M01 Plain (8mm) Washer - Overview. The 90405-ZZ5-M01 Plain (8mm) Washer is a critical component in Honda marine engine systems. It functions primarily as a load distributor and surface protector in mechanical assemblies, helping to maintain equipment reliability and longevity. This plain washer is designed specifically for Honda marine applications where precise fit and durability are paramount. Made to machine-level tolerances, it ensures seamless integration with existing parts, main