For extending the length of threaded bar. Plated in Trivalent Chromium (Cr3) Zinc Standard metric thread" Thread Dia. mm: M20 Socket Size mm: 30 Height mm: 60.0 Thread Type: Metric Finish: Zinc & Clear Cr3 Material: Carbon Steel Timco Hex Connector Nuts - Zinc (Size M20 - 25 Pieces) in Silver