The center pillar stiffener, the front inner upper pillar, the front pillar upper stiffener, the roof front rail, the front side frame extension, the rear frame, the roof side stiffener, and the side sill reinforcement are made from ultra high-strength steel (UHSS) (1500 MPa).

Ultra high-strength steel (UHSS) (1500 MPa) sheet: This is an ultra high-strength material manufacturing procedure. A heated steel sheet is press-formed in the metal mold and then quenched to create high-strength steel.

If ultra high-strength steel is heated, the strength of the steel is reduced. If ultra high-strength steel is damaged, for example, in a collision, and the reinforcement beams or the ultra high-strength steel (UHSS) (1500 MPa) sheet are bent, the beams of the ultra high-strength steel (UHSS) (1500 MPa) sheet may crack when attempting to straighten them. If a door beam is damaged, the whole door assembly must be replaced.

For this reason, the door, bumper reinforcement beams, and the ultra high-strength steel (UHSS) (1500 MPa) sheet should NEVER be repaired; and NEVER be welded by MAG welding; they must be replaced by only spot welding and MIG brazing if they are damaged.