DIN 931 Hex Bolt (ISO 4014) 12.9 Steel

Steel material, poor corrosion resistance.
Partially threaded, metric thread.
Uncoated (ST).
Property class 12.9.
Hex head.

A hex bolt (nut head, hex head bolt) is the most commonly used screw fastener in machine and equipment installations. The head shape provides a good grip, and the tools used for installation provide good grip to tighten the fastener to the correct torque. In everyday language, a hex bolt has many names, such as bolt, screw, machine screw, nut head screw, threaded bolt, or threaded screw, to name a few of the most common. Materials include uncoated or zinc-plated steel (bright zinc, ZN, zinc), hot-dip galvanized (KS, HDG), zinc flake (ZNF), stainless steel (A2), and acid-resistant steel (A4).