On this parts fiche the Washer(5.5x20x1.2) is the most specified component.
A sample from the products for the Rear Combination Lamp (vzr1800z L1 E3) include: Bulb(12v5w,bf150-40160a), Reflector Assy,rr, Lamp Assy,rr Combination, Washer(5.5x20x1.2).
The Suzuki REAR COMBINATION LAMP (VZR1800Z L1 E3) has twenty products enlisted in the schematic.