zinc-plated metal connector SGS audited More than 20 years experience in special fastener ... the material of this kind of nut: Grade3.6,4.6,4.8,5.6,6.8,8.8,9.8,10.9,12 ... ,dacroment),Nickel plated,copper plated,gold plated,chrome(3+Rohs &6+ ) plated,anodic oxidation,etc Dip plating black oxide coating,hot ... so that you could avoid lots ofrisks. zinc-plated metal connector