Standard fastener with hexagonal outer head, easy to tighten with spanner, socket wrench. Available in full thread (DIN933 / GB/T5783) and partial thread (DIN931 / GB/T5782). Strength grades: 4.8, 8.8, 10.9, 12.9. Materials include carbon steel, alloy steel and stainless steel. Various surface treatments: black oxide, galvanizing, hot-dip galvanizing. Widely used in machinery, construction, vehicle manufacturing and equipment assembly.