DIN 931 standard specifies partially threaded hexagon head bolts.The specifications include details such as material,thread type, length, head type, and strength class. DIN 931 hex bolts are commonly made from steel or stainless steel, metric coarse threads, and are available in various lengths. The hexagon head allows for easy tightening with a wrench or socket. Different strength marks like 8.8 or 10.9 indicate the bolt's tensile strength.