Flat DIN433 Washers are the smallest type of flat washer because their outside diameter (OD) is usually just a little more than twice their inside diameter (ID). If you already have a washer and you are trying to match it measure the inside then look for a size slightly smaller that your measurement. For example the inside measurement of the washer you measured is approx 6.50mm you need to look for a M6 washer. If the washer measured 17.25mm internally then you need a M16 Washer. It is aesthetically pleasing to the eye and very practical because of its excellent corrosion protection in most environments. Most products can be identified by the following markings: A2 A2-70 304 or G304 but not all washers are stamped. Stainless steels are largely non-magnetic but it is common for some stainless steel fasteners especially stamped components like washers to show a small degree of magnetism which is a result of work-hardening during the manufacturing process. The use of tools and drills made from conventional steel during the installation of stainless steel fasteners may also lead to problems. Even the hardest of tools can produce debris that leaves minute steel particles on the stainless steel fastener surfaces or in pre-drilled holes. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person and Bolt and Nut Australia is not responsible for any loss claim or damages arising therefrom.