Genuine OEM BMW crankshaft main bearing shell, part number 11218471813. This bearing shell is designed to support the crankshaft within the engine block, reducing friction and wear during high-speed operation. It is engineered with specific metallurgical properties to ensure optimal oil film retention and heat dissipation. Genuine OEM bearings are critical for maintaining factory-specified clearances, which is essential for preventing engine failure and ensuring a long, vibration-free service life.