... special fastener 1,Name:Black steel hex screw;black hex screw;steel hex screw 2,For the similar hex screw,what can we do ... 5052,6061,6063,etc(2),Ability for the surface finish: ElectroplateZinc plated(while,colour,dacroment),Nickel plated,copper ... coating,etc Polishing Grinding and polishing,etc,except mirror finish (3),Ability for the tolerance Roundess0.002mmCylindricity0.003mmRoughnessRa0. ...