Thin Hexagonal Nut Nylon Insert Fine Thread Off-White Nylon 5/8-18 Grade 5

Also known as jam nuts, these are about half the height of standard hex nuts. Use them in low-clearance applications or jam one against another nut to hold it in place. They're suitable for fastening most machinery and equipment when used in conjunction with a standard hex nut. A zinc plating provides corrosion resistance in wet environments.