Metric Coarse - Button Head - Socket Screw - Alloy Steel Grade 12.9 button head socket screws or allen screws. Manufactured ISO Standard 7380 in high tensile 12.9 grade alloy steel. Our button head socket screws are available in black finish or a zinc plated finish for corrosion protection. Suitable for high strength bolting into threaded components and assemblies in manufacturing, mining and engineering industries. Supacheap bolts stock M4, M5, M6, M8 and M10 diameters and lengths to 50mm in certain sizes. Socket button head screw lengths are measured from under the head.