introduction to products：

Black Hex Flange Head Bolts (DIN 6921) are hex - headed fasteners with an integrated flange washer, designed to spread load evenly and prevent loosening in vibration - filled environments. Made from carbon steel (strength grades 8.8, 10.9, 12.9) or alloy steel, they sport a black surface treatment (like black oxide for wear resistance or black zinc for rust protection). The built - in flange means no need for a separate washer, speeding up installation. Following the DIN 6921 standard, they come in sizes from M5 to M30. They’re widely used in automotive (chassis mounts, engine bays), machinery (industrial equipment), and off - road vehicles (suspension setups), providing secure, vibration - fighting fastening.

Instructions for Use：

Install with a matching hex wrench, tightening to the suggested torque (for example, Grade 10.9 bolts need more torque than Grade 8.8). The flange’s serrated or smooth surface grabs the workpiece to stop it from rotating. For upkeep: Clean often with a dry cloth; fix scratched black coating with anti - rust paint. Check the flange for damage — replace bolts if the flange warps or threads strip.

Hebei Duojia Metal Products Co., Ltd. was formerly known as Yonghong Expansion Screw Factory. It has over 25 years of professional experience in manufacturing fasteners. The factory is located in the China Standard Room Industrial Base - Yongnan District, Handan City. It conducts online and offline production and manufacturing of fasteners as well as one-stop sales service business.

The factory covers an area of over 5,000 square meters, and the warehouse covers an area of over 2,000 square meters. In 2022, the company carried out industrial upgrading, standardized the production order of the factory, improved the storage capacity, enhanced safety production capacity, and implemented environmental protection measures. The factory has achieved a preliminary green and environmentally friendly production environment.

The company has cold pressing machines, stamping machines, tapping machines, threading machines, forming machines, spring machines, crimping machines, and welding robots. Its main products are a series of expansion screws known as "wall climbers".

It also produces special-shaped hook products such as wood tooth welding sheep eye ring screws and machine tooth sheep eye ring bolts. In addition, the company has expanded new product types from the end of 2024. It focuses on pre-buried products for the construction industry.

The company has a professional sales team and a professional follow-up team to safeguard your products. The company guarantees the quality of the products it offers and can conduct inspections on the grades. If there are any problems, the company can provide professional after-sales service.

Our export countries include Russia, South Korea, Britain, France, Germany, Italy, Canada, Mexico,Brazil, Argentina, Chile, Australia, Indonesia, Thailand, Singapore, Saudi Arabia, Syria, Egypt, Tanzania.Kenya and other countries. Our products will be spread all over the world!

WHY CHOOSE US?

1.As a factory-direct upplier,we eliminate middleman margis to offer you the most competitive pricing for high-quality fasteners.
2.our factory pass the ISO 9001 and AAA certification .we have the hardness testing and the test of zinc coating thickness for galvanized products.
3.with full contrl over production and logistic,we guarantee on-time delivery even for urgnt orders .
4.our engineering team can customize faseners from prototype to mass production , including unique thread designs and anti-corrosion coatings.
5.From carbon steel hex bolts to high-tensile anchor bolts ,we provide a one-stop solution for all your fastener needs.
6.If any defect is found ,we’ll reship replacements within 3weeks  of our cost .