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 sets crew, as found on much modern machinery. A hex key (otherwise known as an Allen key) is required to fit these fasteners. Conforming to DIN 912 or ISO 4762. Please note that due to manufacturing limitations, all nylon variants of these items are only "similar to" and not "in absolute accordance with" the standard specified.