Also known as an Allen screw or Allen bolt, or simply a cap screw. Socket Head Cap screws are a more modern alternative standard machine fastener to the standard hexagon headed bolt or setscrew, as found on much modern machinery. A hex key (otherwise known as an Allen key) is required to fit these fasteners. Conforming to ISO 4762 or DIN 912, the contact surfaces of this screw or bolt are protected from external damage. Generally manufactured with a partial thread beyond a certain length and nominal diameter combination, but occasionally some stock may include a fully threaded shank at the same combination. A guaranteed fully threaded variant is also available.