Black steel hex screw Process:Mahined and turned Surface:BO SGS audited More than ... fastener 1,Name:Black steel hex screw;black hex screw;steel hex screw 2,For the similar hex screw,what can we do ?(1 ... ), Ability for the material of this kind of hex screw: Grade3.6,4.6,4.8,5.6,6.8 ... hardware fastener ,especially the cutting/turning parts. Black steel hex screw