5/16-18 Grade 8 Nylon Insert Locknut Yellow Zinc Plated . Threads are molded into the nylon insert locking the bolt into place. Nylon Insert Lock Nuts typically have a cased metal outside formed into a hex pattern easily torqued by a wrench or socket. Type NE Grade C. ASME B1.1 UNC and UNF Class 2B thread requirements. Yellow Zinc offers a modest amount of corrosion resistance, slightly higher than that of clear zinc.