... bolt Dia:Min 5mm Surface :BO SGS audited More than 20 years experience in special fastener field 1,Name: Black thread bolt ... ;Thread bolt;Black bolt 2,For the similar bolt,what can we do ?(1), Ability ... for the material of this kind of bolt: Grade3.6,4.6,4.8,5.6,6.8 ... hardware fastener ,especially the cutting/turning parts. Black thread bolt