Genuine OEM BMW Crankcase Ventilation Hose, part number 11157843150. This hose is responsible for routing blow-by gases from the crankcase back into the intake system for combustion. It is constructed from heat-resistant, oil-impermeable materials to withstand the harsh environment of the engine bay. Using a genuine OEM hose is vital to ensure correct routing geometry and a secure connection, preventing vacuum leaks and maintaining optimal engine performance.