Genuine Yamaha 10mm plate washer. 28mm OD and 2mm thick. Also used as rear shock mounting washer for RD125, RD200, XS500, XS750, XS850, XJ650, XJ750, XJ900, XV535, XV1100, XS250, XS400, SR250. This is exactly the right size and appearance for these applications, where sometimes pattern parts are clearly not correct. This is OEM removed from an original Yamaha XJ900 motorcycle. No rust, but marked from use as you can see. Yamaha now supply a substitute part 90201 105R9.