hex head bolt DIN931 1.ISO9001:2008 CERTIFICATION 2.DIN931 DIN933 ISO4014 ASME18.2.1 3.M6-M30 1/4-2'' 4.304 316 321 hex head bolt DIN931 A2 A4 The main products: are stainless steel hex head bolts, hexagon socket setscrews, machine screws, expansion screws, ground screws, U-bolts and others. By using good quality raw materials at home and abroad, we can produce goods according to GB, DIN, ANSI, ...