The class 12.9 alloy steel socket cap screw has a black oxide finish and a flat head with an internal hex drive, and meets Deutsches Institut für Normung DIN 7991 specifications. Class 12.9 alloy steel, composed of quenched and tempered alloy steel, is often used in applications where strength is the primary consideration. The material is magnetic. The black oxide finish offers mild corrosion resistance and lubricity. The flat head is cone shaped for use in countersunk holes and has a flat top that fits flush with the mated surface. The internal hex drive, also known as a hex-socket drive, has a hexagonal slot that requires an Allen key driver, also known as a hex key or Allen wrench.

Socket cap screws are threaded fasteners that have a cap head with an internal socket drive for installing in areas with limited side clearance. These screws are available with a variety of head shapes, which determine how the screw interacts with the mating surface, and drive styles, which determine the type of tool required to install the screw.