Flat Head Socket Cap screws, or simply ‘flat head screws’ are used in machine parts, die fixturing, and especially common for removable panels and parts. Flat Heads are fully countersunk, so they become flush when installed. These are most often used for assembling close tolerance machinery where head clearance is critical. All socket screws (Button Head,Socket CapandFlat Head) are tightened with anAllen key(socket wrench) drive. Available in 12.9 Alloy Steel, A2 Stainless and A4 / 316 Marine Grade Stainless Steel.