DIN 439 MF Hex Nut Low 04. Steel Fine Thread

Material: steel. Strength class 04. Metric fine thread (MF). Uncoated (St), poor weather resistance.

Special nuts are generally considered to be nuts whose design, use, dimensions, or other characteristics differ from a standard hex nut.
Examples include low nuts (thin nuts), flange nuts, castle nuts, rivet nuts, square nuts, diamond nuts (diamond-shaped profile), sheet metal nuts, and weld nuts.
Materials include uncoated or zinc-plated steel (bright zinc, Zn, zinc), stainless steel (A2), and acid-resistant steel (A4).
Choosing the right nut? As a rule, the nut’s hardness, material, and coating should be at least equal to those of the fastener used (bolt, screw).