This metric thread Class 8 bolt is threaded to the head and is made from medium carbon steel, making them useful in mounting motors to machinery. They are also used in automotive and truck repair. These shall be heat treated by quenching in a liquid medium from above the transformation temperature and reheating to a tempering temperature of 425 degrees (C). Proof Load is a minimum of 640 square N/mm with a tensile strength of a minimum of 800 square N/mm. MCS420CFZ88