BMW wanted to meet the requirements of any side crash test. So Ultra-high Strength Steel was used in many different parts of the body structure. The side frames are made with UHSS and the B-Pillar is reinforced with every one’s favorite steel, boron. The B-pillar reinforcement was made of hot formed boron steel. What is good to know about this reinforcement is the distinctly higher wall thickness in the center area than in the upper and lower ends. You may what to put that knowledge under your helmet!