Socket head cap screws, or simply called ‘socket cap screws’ are used in machine parts and are especially common for removable panels and parts. Socket cap screws are the strongest head type and with a round cap with a hex head and are tightened with an Allen key (socket wrench) drive. Socket caps are the general term for Socket Head Cap screws, but loosely also refer to Button Head Socket Cap, and Flat Head Socket Cap screws as well. Button Heads have a round head profile and are less likely to be hit or snagged, while Flat Heads are fully countersunk. We carry 12.9 Alloy steel (in Black Oxide or Zinc plated steel) and both 18-8 (A2) and 304 (A4) Stainless Steel options.