The alloy steel socket cap screw has a plain finish and a button head with an internal hex drive. Alloy steel is often used in applications where strength is the primary consideration. The button head is round with a low profile and short vertical sides, and is suitable for light duty applications. 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.