Double End Bolt,Special 1.ISO,ANSI,CE,JIS,DIN,BS& ... 3.Grade:4.8 ,6.8,8.8,9.8... Double End Bolt,Special Head Bolt,Bolt Maker ,M6 Bolt Dimensions1 ... when you tighten the fasteners by wrench ,key ,bit and spanner.When head become thicker,and then the socket is much ...