DIN 933 Hex Bolt (ISO 4017) 12.9 Steel

Material: steel, poor corrosion resistance.
Fully threaded, metric thread.
Uncoated (ST).
Strength class 12.9.
Hex head.

A hex bolt (nut head, hex head bolt) is the most commonly used screw fastener in machine and equipment assembly. The shape of the head provides a good grip, and the tools used for installation provide a firm hold for tightening the fastener to the correct torque. In everyday language, a hex bolt is known by 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).