The Genuine BMW Radiator Coolant Hose O-Ring - 17128642529 is a small rubber ring that is used to seal the connection between the radiator and the coolant hose in a BMW vehicle. This O-ring is an essential component for maintaining the proper flow of coolant through the system, preventing leaks and ensuring the engine stays at the optimal temperature. It is a genuine BMW part, designed specifically for use in BMW vehicles, ensuring a perfect fit and reliable performance. This O-ring is made of high-quality materials and is built to withstand the harsh conditions of the engine compartment. It is a crucial part for ensuring the overall health and longevity of the cooling system in a BMW vehicle.