Genuine Yamaha 10mm plate washer used top and bottom of the left shock and for the main muffler mounting bolts that go through the footrest bracket on an XS1100. This is exactly the right size for these applications, where sometimes pattern parts are clearly not correct. These are OEM removed from an original Yamaha XS1100 motorcycle. No rust, but marked from use as you can see. Price is for one. Also fit other bikes listed.