GB21 small hexagon head bolts are standard fasteners used in automobile manufacturing, mechanical equipment, building structures and other fields. The bolts comply with the GB21 national standard and have excellent mechanical properties and reliable connection strength. Its small hexagon head design can provide higher torque transmission in a limited space while optimizing installation efficiency. GB21 small hexagon head bolts are made of high-strength alloy steel and undergo a heat treatment process to improve wear resistance and tensile strength to meet the high requirements of the automotive industry for fasteners. The surface treatment of the bolts can be galvanized, electrophoresed or other anti-corrosion processes as required to enhance rust resistance and improve durability. In the automotive field, GB21 small hexagon head bolts are often used in key parts such as engine components, chassis connections, suspension systems, etc., providing vehicles with safe and reliable fastening solutions Key Advantages for Your Applications: Standardized Reliability: Complies with the GB21 national standard, ensuring consistent performance. High Mechanical Strength: Manufactured from high-strength alloy steel and heat-treated for exceptional durability. Efficient Torque Transmission: Small hexagon head allows for high torque in limited spaces. Optimized Installation Efficiency: Streamlined head design facilitates faster assembly. Enhanced Wear Resistance: Heat treatment improves the bolt's ability to withstand friction and wear. Customizable Corrosion Protection: Galvanizing, electrophoresis, and other options available. Secure and Reliable Connections: Ensures the integrity and safety of critical assemblies. Ideal for: Engine Components: Securing cylinder heads, manifolds, brackets, and other critical engine parts. Chassis Connections: Joining frame members, crossmembers, and other structural elements. Suspension Systems: Fastening control arms, struts, linkages, and other suspension components. Transmission Assemblies: Securing internal components and housings. Braking Systems: Attaching calipers, rotors, and other braking components. Automotive Interior and Exterior: Securing panels, trim, and other non-structural elements where space is a concern. Mechanical Equipment: General fastening in machinery where space efficiency is required. Building Structures: Certain light-duty structural applications where a smaller head profile is beneficial. Product NameStandardMaterialDiameter (Thread Size)LengthHexagon Head BoltGB/T 5782-2016Carbon Steel, Grade 8.8M516 mmHexagon Head BoltGB/T 5782-2016Carbon Steel, GalvanizedM620 mmHexagon Head BoltGB/T 5782-2016Stainless Steel A2-70M825 mmHexagon Head BoltGB/T 5782-2016Alloy Steel, Grade 10.9M1030-100 mmHexagon Head BoltGB/T 5782-2016Carbon Steel, Black OxideM1240-120 mmHexagon Head BoltASME B18.2.1ASTM A307, Grade B1/4"1" (25.4 mm)Hexagon Head BoltASME B18.2.1ASTM A325, Type 15/16"1.5" (38 mm)Hexagon Head BoltASME B18.2.1ASTM A193 B73/8"2" (50.8 mm)Hexagon Head BoltASME B18.2.1Stainless Steel 3161/2"3" (76.2 mm)Hexagon Head BoltDIN 931C45 Steel, GalvanizedM620-200 mmHexagon Head BoltDIN 9338.8 Steel, PlainM825-200 mmHexagon Head BoltISO 4014Steel, Grade 8.8M1030-300 mmHexagon Head BoltISO 4017Stainless Steel A4-80M1240-300 mmHexagon Head BoltJIS B 1180SCM435 Alloy SteelM620-150 mmHexagon Head BoltJIS B 1180SUS304 Stainless SteelM825-150 mmHexagon Head BoltANSI B18.2.3.6MASTM A490, GalvanizedM1650-300 mmHexagon Head BoltBS 3692EN 14399-4 Grade 10.9M2060-300 mm