This listing is for new Serrated Hex Flange Lock Nuts. These are made from Case Hardened Zinc Plated Steel (Zinc Cr+3 RoHS Compliant Product). Available Sizes: Coarse Fine #6-32 #8-32 #10-24 #10-32 (fine) 1/4"-20 1/4"-28 (fine) 5/16"-18 5/16"-24 (fine)