DIN 931 hexagon head screw, M20 x 330, en 10204 3.1 certificate, Article number 9311020330GEO5AC. Property class / material: steel 10.9, surface finish zinc flake, silver. Hexagon Head Screw manufactured to DIN 931 with ISO metric (M) thread, coarse pitch, partially threaded. Standard parts to the same standard, property class, dimensions and surface finish are interchangeable between manufacturers; confirm the controlling standard revision, any class-society or application approval, and the mating thread before substitution.