1. DIN 6921 is a standard specification developed by the Deutsches Institut für Normung (DIN) that pertains to hex flange bolts with a reduced head. This standard outlines the dimensions, materials, and technical requirements for these types of fasteners. The inclusion of a flange on the bolt head serves to distribute the clamping load over a larger area, providing additional stability and preventing the bolt from loosening under vibration or other external forces. DIN 6921 bolts are commonly used in applications where a high degree of reliability and strength is required, such as automotive, construction, and machinery industries. Compliance with this standard ensures interchangeability and compatibility between different manufacturers and guarantees the quality and performance of the fasteners.