DIN6921 hexagonal flange head bolt is fully threaded bolt with integrated serrated flange. The serrations under flange provide anti-slip and anti-loosening function, separate washer is not required. Carbon steel grade 8.8,10.9 or stainless steel A2/A4. Surface: zinc plated, black oxide, hot dip galvanized. Sizes M5~M16. Widely used for solar mounting systems, seismic brackets and machinery assembly.