Genuine Yamaha 8mm spring washers used on the ten studs on the back of the final drive. They are exactly the right size for this application, where sometimes pattern parts are clearly not correct. The width of the washer and the thickness of the washer is different to other 8mm washers on the motorcycle and different to pattern parts. These are OEM removed from an original Yamaha XS1100 motorcycle. No rust, but marked from use as you can see. Yamaha now supply 92907 08100 as a substitute part. Price is for five. Ten available. This is a standard Yamaha part and fits virtually every Yamaha model.