M3 Cap Head 12.9 Range DIN 912 ~ Socket Cap Head 12.9 Grade Socket Cap Head Screws 12.9 Grade (High Tensile) Socket cap head screws are all 12.9 grade high tensile steel with the recognised standard - DIN 912. These are the highest strength grade of screw available in M3, typically used on the Schumacher CAT for the the front/rear inner hinge pin blocks, due to their tensile strength over lighter grades like stainless steel.