BZP Steel Plain Washer- Metric Plain washers or flat washers as they a commonly refered to are standard spacing washers used on thousands of industrial and domestic applications. A plain washer (or 'flat washer') is a flat annulus or ring, often of metal, used to spread the load of a screwed fastening. Additionally, a plain washer may be used when the hole is a larger diameter than the fixing nut. Steel washer zinc plated,for ISO metric fastenersMetric to BS4320 Form ADIN 125 A M10 Washer