Hex socket countersunk head screw is fastener with tapered countersunk head and internal hex drive. The head can sink fully flush into workpiece surface. It uses hex allen key for tightening. Common strength classes: 8.8,10.9,12.9. Material: carbon steel / alloy steel; finishes: blue-white zinc plated, color zinc plated, black oxide, Dacromet. Widely used in mould, machinery, metal fixture assembly.