Size: M3 M4 M5 M6 M8 M10 M12 M14 M16 M18 M20. -Material: A2 Stainless Steel. -Thickness: 1mm 1.5mm 2mm 3mm 4mm 5mm. Efficient Effect Square washer disperses the pressure of surface to protect the connecting surface, and prevent the nut from loosening, which is highly protective.
eBay