... years experience 1,Name: Steel hex coupling;steel coupling;hex coupling2,For the similar coupling ,what can we do ?(1), ... Ability for the material of this kind of coupling : Grade3.6,4.6,4.8,5.6, ... 3),Ability for the tolerance Roundess0.002mmCylindricity0.003mmRoughnessRa0.32Straightness0.01/200mm 3,How about the packing details?Plastic bags ... ,especially the cutting/turning parts. Steel hex coupling