... 20 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 : Grade3.6,4.6,4.8,5.6,6 ... 4140,G51150,etcStainless steel201,202,301,302,303,304,316,310,430,etcBrassC28000,C37710,C3450,C27200,etcBronzeC51900,C60600,C17200 ... fastener ,especially the cutting/turning parts. Steel hex coupling