Genuine OEM BMW Crankcase Ventilation Hose, part number 11151720390. This hose is responsible for routing crankcase gases to ensure proper engine ventilation. It is typically made from durable rubber to withstand engine bay temperatures and resist degradation. The correct routing and sealing of crankcase gases are vital for engine health and emissions control, preventing pressure buildup and oil contamination. Genuine OEM parts ensure exact fitment and material integrity for reliable performance.